diff --git a/src/main/java/nl/sander/beejava/Compiler.java b/src/main/java/nl/sander/beejava/Compiler.java
index e755772..534255a 100644
--- a/src/main/java/nl/sander/beejava/Compiler.java
+++ b/src/main/java/nl/sander/beejava/Compiler.java
@@ -2,7 +2,7 @@ package nl.sander.beejava;
 
 import nl.sander.beejava.api.BeeClass;
 import nl.sander.beejava.constantpool.ConstantPool;
-import nl.sander.beejava.constantpool.entry.ConstantPoolEntry;
+import nl.sander.beejava.constantpool.entry.NodeConstant;
 import nl.sander.beejava.util.ByteBuf;
 
 import java.util.Set;
@@ -28,7 +28,7 @@ public class Compiler {
         buf.add(beeClass.getClassFileVersion().getMinor());
         buf.add(beeClass.getClassFileVersion().getMajor());
 
-        Set<ConstantPoolEntry> constantTree = constantTreeCreator.createConstantTree(beeClass);
+        Set<NodeConstant> constantTree = constantTreeCreator.createConstantTree(beeClass);
         ConstantPool constantPool = constantPoolCreator.createConstantPool(constantTree);
 
         buf.add(constantPool.getBytes());
diff --git a/src/main/java/nl/sander/beejava/ConstantPoolCreator.java b/src/main/java/nl/sander/beejava/ConstantPoolCreator.java
index c77b38b..552c007 100644
--- a/src/main/java/nl/sander/beejava/ConstantPoolCreator.java
+++ b/src/main/java/nl/sander/beejava/ConstantPoolCreator.java
@@ -1,7 +1,7 @@
 package nl.sander.beejava;
 
 import nl.sander.beejava.constantpool.ConstantPool;
-import nl.sander.beejava.constantpool.entry.ConstantPoolEntry;
+import nl.sander.beejava.constantpool.entry.NodeConstant;
 
 import java.util.Set;
 
@@ -9,10 +9,11 @@ import java.util.Set;
  * Transforms the hierachical constant tree into a flat datastructure. The walks the tree adding indexes to each element.
  */
 public class ConstantPoolCreator {
-    private ConstantPool constantPool;
-    private int index;
+    private ConstantPool constantPool; // the constant pool that is being created
+    private int index; // the current index that will be assigned to a constant pool entry. It needs to be unique for each entry.
+    // References to other elements in the pool are made through indexes, so they have to be valid to guarantee that the class can be loaded by the JVM.
 
-    public ConstantPool createConstantPool(Set<ConstantPoolEntry> constantTree) {
+    public ConstantPool createConstantPool(Set<NodeConstant> constantTree) {
         constantPool = new ConstantPool();
         constantPool.add(null); // dummy element to align it's index with the indexes in the elements themselves
         index = 0;
@@ -20,26 +21,26 @@ public class ConstantPoolCreator {
         return constantPool;
     }
 
-    private void updateToplevelElements(Set<ConstantPoolEntry> children) {
-        for (ConstantPoolEntry child : children) {
+    private void updateToplevelElements(Set<NodeConstant> children) {
+        for (NodeConstant child : children) {
             addToPool(child);
             updateChildElements(child.getChildren());
             // first the complete toplevel element including it's children, then next toplevel element
         }
     }
 
-    private void updateChildElements(Set<ConstantPoolEntry> children) {
+    private void updateChildElements(Set<NodeConstant> children) {
         // first all direct children
-        for (ConstantPoolEntry child : children) {
+        for (NodeConstant child : children) {
             addToPool(child);
         }
         // then further lineage
-        for (ConstantPoolEntry child : children) {
+        for (NodeConstant child : children) {
             updateChildElements(child.getChildren());
         }
     }
 
-    private void addToPool(ConstantPoolEntry entry) {
+    private void addToPool(NodeConstant entry) {
         index += 1;
         entry.setIndex(index);
         constantPool.add(entry);
diff --git a/src/main/java/nl/sander/beejava/ConstantTreeCreator.java b/src/main/java/nl/sander/beejava/ConstantTreeCreator.java
index e5ac480..bea2cd6 100644
--- a/src/main/java/nl/sander/beejava/ConstantTreeCreator.java
+++ b/src/main/java/nl/sander/beejava/ConstantTreeCreator.java
@@ -18,7 +18,7 @@ import java.util.Set;
  * also TODO make sure entries aren't duplicates
  */
 public class ConstantTreeCreator {
-    private final Set<ConstantPoolEntry> constantTree = new LinkedHashSet<>();
+    private final Set<NodeConstant> constantTree = new LinkedHashSet<>();
     private BeeClass beeClass;
 
     /**
@@ -28,7 +28,7 @@ public class ConstantTreeCreator {
      * @param beeClass the Class object for which the constant pool needs to be created
      * @return a Set of constant pool entries
      */
-    public Set<ConstantPoolEntry> createConstantTree(BeeClass beeClass) {
+    public Set<NodeConstant> createConstantTree(BeeClass beeClass) {
         constantTree.clear();
         this.beeClass = beeClass;
         beeClass.getConstructors().forEach(this::updateConstantTree);
@@ -55,23 +55,23 @@ public class ConstantTreeCreator {
     }
 
     private void addMethod(CodeLine codeline) {
-        constantTree.add(new MethodRefEntry(createClassName(codeline), createMethodNameAndType(codeline)));
+        constantTree.add(new ConstantMethodRef(createClassName(codeline), createMethodNameAndType(codeline)));
     }
 
     private void addField(CodeLine codeline) {
-        constantTree.add(new FieldRefEntry(createClassName(codeline), createFieldNameAndType(codeline)));
+        constantTree.add(new ConstantFieldRef(createClassName(codeline), createFieldNameAndType(codeline)));
     }
 
-    private NameAndTypeEntry createMethodNameAndType(CodeLine codeline) {
-        return new NameAndTypeEntry(new Utf8Entry(codeline.getMethodName()), new Utf8Entry(codeline.getMethodSignature()));
+    private ConstantNameAndType createMethodNameAndType(CodeLine codeline) {
+        return new ConstantNameAndType(new ConstantUtf8(codeline.getMethodName()), new ConstantUtf8(codeline.getMethodSignature()));
     }
 
-    private NameAndTypeEntry createFieldNameAndType(CodeLine codeline) {
-        return new NameAndTypeEntry(new Utf8Entry(codeline.getField().getName()), new Utf8Entry(TypeMapper.map(codeline.getField().getType())));
+    private ConstantNameAndType createFieldNameAndType(CodeLine codeline) {
+        return new ConstantNameAndType(new ConstantUtf8(codeline.getField().getName()), new ConstantUtf8(TypeMapper.map(codeline.getField().getType())));
     }
 
-    private ClassEntry createClassName(CodeLine codeline) {
-        return new ClassEntry(new Utf8Entry(internalName(getNameOfClass(codeline))));
+    private ConstantClass createClassName(CodeLine codeline) {
+        return new ConstantClass(new ConstantUtf8(internalName(getNameOfClass(codeline))));
     }
 
     private String getNameOfClass(CodeLine codeline) {
diff --git a/src/main/java/nl/sander/beejava/constantpool/ConstantPool.java b/src/main/java/nl/sander/beejava/constantpool/ConstantPool.java
index 3af37e1..3ac6e0a 100644
--- a/src/main/java/nl/sander/beejava/constantpool/ConstantPool.java
+++ b/src/main/java/nl/sander/beejava/constantpool/ConstantPool.java
@@ -1,14 +1,14 @@
 package nl.sander.beejava.constantpool;
 
-import nl.sander.beejava.constantpool.entry.ConstantPoolEntry;
+import nl.sander.beejava.constantpool.entry.NodeConstant;
 
 import java.util.ArrayList;
 import java.util.List;
 
 public class ConstantPool {
-    private final List<ConstantPoolEntry> entries=new ArrayList<>();
+    private final List<NodeConstant> entries=new ArrayList<>();
 
-    public int getIndex(ConstantPoolEntry entry){
+    public int getIndex(NodeConstant entry){
         for (int i=0; i<entries.size(); i++){
             if (entries.get(i)==entry){
                 return i+1;
@@ -17,11 +17,7 @@ public class ConstantPool {
         return -1;
     }
 
-    public void add(int index, ConstantPoolEntry entry){
-        entries.add(index, entry);
-    }
-
-    public void add(ConstantPoolEntry entry){
+    public void add(NodeConstant entry){
         entries.add(entry);
     }
 
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ClassEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantClass.java
similarity index 62%
rename from src/main/java/nl/sander/beejava/constantpool/entry/ClassEntry.java
rename to src/main/java/nl/sander/beejava/constantpool/entry/ConstantClass.java
index 79c8aec..528a521 100644
--- a/src/main/java/nl/sander/beejava/constantpool/entry/ClassEntry.java
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantClass.java
@@ -1,9 +1,9 @@
 package nl.sander.beejava.constantpool.entry;
 
-public class ClassEntry extends ConstantPoolEntry {
-    private final Utf8Entry name;
+public class ConstantClass extends NodeConstant {
+    private final ConstantUtf8 name;
 
-    public ClassEntry(Utf8Entry name) {
+    public ConstantClass(ConstantUtf8 name) {
         super(name);
         this.name = name;
     }
@@ -18,4 +18,9 @@ public class ClassEntry extends ConstantPoolEntry {
                 "nameIndex=" + getNameIndex() +
                 '}';
     }
+
+    @Override
+    public int getTag() {
+        return 7;
+    }
 }
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantDouble.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantDouble.java
new file mode 100644
index 0000000..100eac7
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantDouble.java
@@ -0,0 +1,14 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantDouble extends LeafConstant {
+    private final double doubleVal;
+
+    public ConstantDouble(double doubleVal) {
+        this.doubleVal = doubleVal;
+    }
+
+    @Override
+    public int getTag() {
+        return 6;
+    }
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantDynamic.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantDynamic.java
new file mode 100644
index 0000000..85093d2
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantDynamic.java
@@ -0,0 +1,20 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantDynamic extends NodeConstant {
+    private final int bootstrapMethodIndex; // TODO
+    private final ConstantNameAndType nameAndType;
+
+    public ConstantDynamic(int bootstrapMethodIndex, ConstantNameAndType nameAndType) {
+        this.bootstrapMethodIndex = bootstrapMethodIndex;
+        this.nameAndType = nameAndType;
+    }
+
+    @Override
+    public int getTag() {
+        return 17;
+    }
+
+    public int getNameAndTypeIndex(){
+        return nameAndType.getIndex();
+    }
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantFieldRef.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantFieldRef.java
new file mode 100644
index 0000000..c93e5e1
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantFieldRef.java
@@ -0,0 +1,33 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantFieldRef extends NodeConstant {
+    private final ConstantClass constantClass;
+    private final ConstantNameAndType constantNameAndType;
+
+    public ConstantFieldRef(ConstantClass constantClass, ConstantNameAndType constantNameAndType) {
+        super(constantClass, constantNameAndType);
+        this.constantClass = constantClass;
+        this.constantNameAndType = constantNameAndType;
+    }
+
+    public int getClassIndex() {
+        return constantClass.getIndex();
+    }
+
+    public int getNameAndTypeIndex() {
+        return constantNameAndType.getIndex();
+    }
+
+    @Override
+    public String toString() {
+        return "FieldRefEntry{" +
+                "classIndex=" + getClassIndex() +
+                ", nameAndTypeIndex=" + getNameAndTypeIndex() +
+                '}';
+    }
+
+    @Override
+    public int getTag() {
+        return 9;
+    }
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/FloatEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantFloat.java
similarity index 62%
rename from src/main/java/nl/sander/beejava/constantpool/entry/FloatEntry.java
rename to src/main/java/nl/sander/beejava/constantpool/entry/ConstantFloat.java
index 2c3e962..44483b5 100644
--- a/src/main/java/nl/sander/beejava/constantpool/entry/FloatEntry.java
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantFloat.java
@@ -1,9 +1,9 @@
 package nl.sander.beejava.constantpool.entry;
 
-public class FloatEntry extends LeafEntry {
+public class ConstantFloat extends LeafConstant {
     private final float floatVal;
 
-    public FloatEntry(float floatVal) {
+    public ConstantFloat(float floatVal) {
         this.floatVal = floatVal;
     }
 
@@ -13,4 +13,9 @@ public class FloatEntry extends LeafEntry {
                 "floatVal=" + floatVal +
                 '}';
     }
+
+    @Override
+    public int getTag() {
+        return 4;
+    }
 }
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/IntEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantInteger.java
similarity index 61%
rename from src/main/java/nl/sander/beejava/constantpool/entry/IntEntry.java
rename to src/main/java/nl/sander/beejava/constantpool/entry/ConstantInteger.java
index cab2d89..201af2b 100644
--- a/src/main/java/nl/sander/beejava/constantpool/entry/IntEntry.java
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantInteger.java
@@ -1,9 +1,9 @@
 package nl.sander.beejava.constantpool.entry;
 
-public class IntEntry extends LeafEntry {
+public class ConstantInteger extends LeafConstant {
     private final int intVal;
 
-    public IntEntry(int integer) {
+    public ConstantInteger(int integer) {
         this.intVal = integer;
     }
 
@@ -13,4 +13,9 @@ public class IntEntry extends LeafEntry {
                 "intVal=" + intVal +
                 '}';
     }
+
+    @Override
+    public int getTag() {
+        return 3;
+    }
 }
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantInterfaceMethodRef.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantInterfaceMethodRef.java
new file mode 100644
index 0000000..9cd3c0d
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantInterfaceMethodRef.java
@@ -0,0 +1,25 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantInterfaceMethodRef extends NodeConstant {
+    private final ConstantClass constantClass;
+    private final ConstantNameAndType constantNameAndType;
+
+    public ConstantInterfaceMethodRef(ConstantClass constantClass, ConstantNameAndType constantNameAndType) {
+        super(constantClass, constantNameAndType);
+        this.constantClass = constantClass;
+        this.constantNameAndType = constantNameAndType;
+    }
+
+    public int getClassIndex(){
+        return constantClass.getIndex();
+    }
+
+    public int getNameAndTypeIndex(){
+        return constantNameAndType.getIndex();
+    }
+
+    @Override
+    public int getTag() {
+        return 11;
+    }
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantInvokeDynamic.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantInvokeDynamic.java
new file mode 100644
index 0000000..187599a
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantInvokeDynamic.java
@@ -0,0 +1,26 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantInvokeDynamic extends NodeConstant {
+    private final int bootstrapMethodAttrIndex; //??
+    private final ConstantNameAndType constantNameAndType;
+
+    public ConstantInvokeDynamic(int bootstrapMethodAttrIndex, ConstantNameAndType constantNameAndType) {
+        this.bootstrapMethodAttrIndex = bootstrapMethodAttrIndex;
+        this.constantNameAndType = constantNameAndType;
+    }
+
+
+    @Override
+    public String toString() {
+        return "InvokeDynamicEntry{" +
+                "bootstrapMethodAttrIndex=" + bootstrapMethodAttrIndex +
+                ", nameAndTypeIndex=" + constantNameAndType.getIndex() +
+                '}';
+    }
+
+    @Override
+    public int getTag() {
+        return 18;
+    }
+}
+//TODO implement later
\ No newline at end of file
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/LongEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantLong.java
similarity index 63%
rename from src/main/java/nl/sander/beejava/constantpool/entry/LongEntry.java
rename to src/main/java/nl/sander/beejava/constantpool/entry/ConstantLong.java
index daaed0c..c951987 100644
--- a/src/main/java/nl/sander/beejava/constantpool/entry/LongEntry.java
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantLong.java
@@ -1,10 +1,10 @@
 package nl.sander.beejava.constantpool.entry;
 
-public class LongEntry extends LeafEntry {
+public class ConstantLong extends LeafConstant {
 
     private final long longVal;
 
-    public LongEntry(long longVal) {
+    public ConstantLong(long longVal) {
         this.longVal = longVal;
     }
 
@@ -14,4 +14,9 @@ public class LongEntry extends LeafEntry {
                 "longVal=" + longVal +
                 '}';
     }
+
+    @Override
+    public int getTag() {
+        return 5;
+    }
 }
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantMethodHandle.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantMethodHandle.java
new file mode 100644
index 0000000..74f5c3c
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantMethodHandle.java
@@ -0,0 +1,32 @@
+package nl.sander.beejava.constantpool.entry;
+
+//TODO implement later
+public class ConstantMethodHandle extends NodeConstant {
+    private final int referenceKind;
+
+    // only 1 of these can be present:
+    private ConstantFieldRef constantFieldRef;
+    private ConstantMethodRef constantMethodRef;
+    private ConstantInterfaceMethodRef constantInterfaceMethodRef;
+
+    public ConstantMethodHandle(int referenceKind) {
+        this.referenceKind = referenceKind;
+    }
+
+    @Override
+    public String toString() {
+        return "MethodHandleEntry{" +
+                "referenceKind=" + referenceKind +
+                ", referenceIndex=" + getReferenceIndex() +
+                '}';
+    }
+
+    private int getReferenceIndex() {
+        return 0; //TODO implement
+    }
+
+    @Override
+    public int getTag() {
+        return 15;
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantMethodRef.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantMethodRef.java
new file mode 100644
index 0000000..9181c00
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantMethodRef.java
@@ -0,0 +1,25 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantMethodRef extends NodeConstant {
+    private final ConstantClass constantClass;
+    private final ConstantNameAndType constantNameAndType;
+
+    public ConstantMethodRef(ConstantClass constantClass, ConstantNameAndType constantNameAndType) {
+        super(constantClass, constantNameAndType);
+        this.constantClass = constantClass;
+        this.constantNameAndType = constantNameAndType;
+    }
+
+    public int getClassIndex() {
+        return constantClass.getIndex();
+    }
+
+    public int getNameAndTypeIndex() {
+        return constantNameAndType.getIndex();
+    }
+
+    @Override
+    public int getTag() {
+        return 10;
+    }
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantMethodType.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantMethodType.java
new file mode 100644
index 0000000..57efdb6
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantMethodType.java
@@ -0,0 +1,21 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantMethodType extends NodeConstant {
+    private final ConstantUtf8 methodDescriptor;
+
+    public ConstantMethodType(ConstantUtf8 methodDescriptor) {
+        this.methodDescriptor = methodDescriptor;
+    }
+
+    @Override
+    public String toString() {
+        return "MethodTypeEntry{" +
+                "methodDescriptor=" + methodDescriptor +
+                '}';
+    }
+
+    @Override
+    public int getTag() {
+        return 16;
+    }
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantModule.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantModule.java
new file mode 100644
index 0000000..1dfdb93
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantModule.java
@@ -0,0 +1,16 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantModule extends NodeConstant {
+
+    private final ConstantUtf8 nameEntry;
+
+    public ConstantModule(ConstantUtf8 nameEntry) {
+        super(nameEntry);
+        this.nameEntry = nameEntry;
+    }
+
+    @Override
+    public int getTag() {
+        return 19;
+    }
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/NameAndTypeEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantNameAndType.java
similarity index 64%
rename from src/main/java/nl/sander/beejava/constantpool/entry/NameAndTypeEntry.java
rename to src/main/java/nl/sander/beejava/constantpool/entry/ConstantNameAndType.java
index 3f3b54c..3b083b7 100644
--- a/src/main/java/nl/sander/beejava/constantpool/entry/NameAndTypeEntry.java
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantNameAndType.java
@@ -1,10 +1,10 @@
 package nl.sander.beejava.constantpool.entry;
 
-public class NameAndTypeEntry extends ConstantPoolEntry {
-    private final Utf8Entry name;
-    private final Utf8Entry type;
+public class ConstantNameAndType extends NodeConstant {
+    private final ConstantUtf8 name;
+    private final ConstantUtf8 type;
 
-    public NameAndTypeEntry(Utf8Entry name, Utf8Entry type) {
+    public ConstantNameAndType(ConstantUtf8 name, ConstantUtf8 type) {
         super(name,type);
         this.name = name;
         this.type = type;
@@ -26,4 +26,9 @@ public class NameAndTypeEntry extends ConstantPoolEntry {
                 ", typeIndex=" + getTypeIndex() +
                 '}';
     }
+
+    @Override
+    public int getTag() {
+        return 12;
+    }
 }
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantPackage.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantPackage.java
new file mode 100644
index 0000000..fd7150f
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantPackage.java
@@ -0,0 +1,19 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantPackage extends NodeConstant {
+    private final ConstantUtf8 name;
+
+    public ConstantPackage(ConstantUtf8 name) {
+        super(name);
+        this.name = name;
+    }
+
+    public int getNameIndex() {
+        return name.getIndex();
+    }
+
+    @Override
+    public int getTag() {
+        return 20;
+    }
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantPoolEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantPoolEntry.java
deleted file mode 100644
index 9df1555..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantPoolEntry.java
+++ /dev/null
@@ -1,27 +0,0 @@
-package nl.sander.beejava.constantpool.entry;
-
-import java.util.Arrays;
-import java.util.LinkedHashSet;
-import java.util.Set;
-
-public abstract class ConstantPoolEntry {
-    protected final Set<ConstantPoolEntry> children;
-    private int index;
-
-    protected ConstantPoolEntry(ConstantPoolEntry... children) {
-        this.children = new LinkedHashSet<>();
-        this.children.addAll(Arrays.asList(children)); // java8 way destroys order, not desastrous, but I like to preserve it.
-    }
-
-    public int getIndex() {
-        return index;
-    }
-
-    public void setIndex(int index) {
-        this.index = index;
-    }
-
-    public Set<ConstantPoolEntry> getChildren() {
-        return children;
-    }
-}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/StringEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantString.java
similarity index 60%
rename from src/main/java/nl/sander/beejava/constantpool/entry/StringEntry.java
rename to src/main/java/nl/sander/beejava/constantpool/entry/ConstantString.java
index a53ef09..d38fc6d 100644
--- a/src/main/java/nl/sander/beejava/constantpool/entry/StringEntry.java
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantString.java
@@ -1,9 +1,9 @@
 package nl.sander.beejava.constantpool.entry;
 
-public class StringEntry extends ConstantPoolEntry {
-    private final Utf8Entry utf8;
+public class ConstantString extends NodeConstant {
+    private final ConstantUtf8 utf8;
 
-    public StringEntry(Utf8Entry utf8) {
+    public ConstantString(ConstantUtf8 utf8) {
         this.utf8 = utf8;
     }
 
@@ -17,4 +17,9 @@ public class StringEntry extends ConstantPoolEntry {
                 "utf8Index=" + getUtf8Index() +
                 '}';
     }
+
+    @Override
+    public int getTag() {
+        return 8;
+    }
 }
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ConstantUtf8.java b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantUtf8.java
new file mode 100644
index 0000000..4c5a948
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/ConstantUtf8.java
@@ -0,0 +1,25 @@
+package nl.sander.beejava.constantpool.entry;
+
+public class ConstantUtf8 extends LeafConstant {
+    private final String value;
+
+    public ConstantUtf8(String utf8) {
+        this.value = utf8;
+    }
+
+    public String getUtf8() {
+        return value;
+    }
+
+    @Override
+    public String toString() {
+        return "Utf8Entry{" +
+                "value='" + value + '\'' +
+                '}';
+    }
+
+    @Override
+    public int getTag() {
+        return 1;
+    }
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/DoubleEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/DoubleEntry.java
deleted file mode 100644
index d586b03..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/DoubleEntry.java
+++ /dev/null
@@ -1,10 +0,0 @@
-package nl.sander.beejava.constantpool.entry;
-
-public class DoubleEntry extends LeafEntry {
-    private final double doubleVal;
-
-    public DoubleEntry(double doubleVal) {
-        this.doubleVal = doubleVal;
-    }
-
-}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/FieldRefEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/FieldRefEntry.java
deleted file mode 100644
index 21ea947..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/FieldRefEntry.java
+++ /dev/null
@@ -1,28 +0,0 @@
-package nl.sander.beejava.constantpool.entry;
-
-public class FieldRefEntry extends ConstantPoolEntry {
-    private final ClassEntry classEntry;
-    private final NameAndTypeEntry nameAndTypeEntry;
-
-    public FieldRefEntry(ClassEntry classEntry, NameAndTypeEntry nameAndTypeEntry) {
-        super(classEntry, nameAndTypeEntry);
-        this.classEntry = classEntry;
-        this.nameAndTypeEntry = nameAndTypeEntry;
-    }
-
-    public int getClassIndex() {
-        return classEntry.getIndex();
-    }
-
-    public int getNameAndTypeIndex() {
-        return nameAndTypeEntry.getIndex();
-    }
-
-    @Override
-    public String toString() {
-        return "FieldRefEntry{" +
-                "classIndex=" + getClassIndex() +
-                ", nameAndTypeIndex=" + getNameAndTypeIndex() +
-                '}';
-    }
-}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/InterfaceMethodRefEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/InterfaceMethodRefEntry.java
deleted file mode 100644
index c505f26..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/InterfaceMethodRefEntry.java
+++ /dev/null
@@ -1,20 +0,0 @@
-package nl.sander.beejava.constantpool.entry;
-
-public class InterfaceMethodRefEntry extends ConstantPoolEntry {
-    private final ClassEntry classEntry;
-    private final NameAndTypeEntry nameAndTypeEntry;
-
-    public InterfaceMethodRefEntry(ClassEntry classEntry, NameAndTypeEntry nameAndTypeEntry) {
-        super(classEntry,nameAndTypeEntry);
-        this.classEntry = classEntry;
-        this.nameAndTypeEntry = nameAndTypeEntry;
-    }
-
-    public int getClassIndex(){
-        return classEntry.getIndex();
-    }
-
-    public int getNameAndTypeIndex(){
-        return nameAndTypeEntry.getIndex();
-    }
-}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/InvokeDynamicEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/InvokeDynamicEntry.java
deleted file mode 100644
index a4f544f..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/InvokeDynamicEntry.java
+++ /dev/null
@@ -1,17 +0,0 @@
-//package nl.sander.beejava.constantpool.entry;
-//
-//public class InvokeDynamicEntry extends ConstantPoolEntry {
-//    private final int bootstrapMethodAttrIndex; //??
-//    private final NameAndTypeEntry nameAndTypeEntry;
-//
-//
-//
-//    @Override
-//    public String toString() {
-//        return "InvokeDynamicEntry{" +
-//                "bootstrapMethodAttrIndex=" + bootstrapMethodAttrIndex +
-//                ", nameAndTypeIndex=" + nameAndTypeIndex +
-//                '}';
-//    }
-//}
-//TODO implement later
\ No newline at end of file
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/LeafEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/LeafConstant.java
similarity index 52%
rename from src/main/java/nl/sander/beejava/constantpool/entry/LeafEntry.java
rename to src/main/java/nl/sander/beejava/constantpool/entry/LeafConstant.java
index 38ac9aa..fb73e65 100644
--- a/src/main/java/nl/sander/beejava/constantpool/entry/LeafEntry.java
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/LeafConstant.java
@@ -3,9 +3,12 @@ package nl.sander.beejava.constantpool.entry;
 import java.util.Collections;
 import java.util.Set;
 
-public class LeafEntry extends ConstantPoolEntry {
+/**
+ * Is a constant without children
+ */
+public abstract class LeafConstant extends NodeConstant {
     @Override
-    public Set<ConstantPoolEntry> getChildren() {
+    public Set<NodeConstant> getChildren() {
         return Collections.emptySet();
     }
 }
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/MethodHandleEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/MethodHandleEntry.java
deleted file mode 100644
index e53f065..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/MethodHandleEntry.java
+++ /dev/null
@@ -1,21 +0,0 @@
-//package nl.sander.beejava.constantpool.entry;
-//
-//public class MethodHandleEntry extends ConstantPoolEntry {
-//    private final int referenceKind;
-//    private final int referenceIndex;
-//
-//    public MethodHandleEntry(int referenceKind, int referenceIndex) {
-//        this.referenceKind = referenceKind;
-//        this.referenceIndex = referenceIndex;
-//    }
-//
-//    @Override
-//    public String toString() {
-//        return "MethodHandleEntry{" +
-//                "referenceKind=" + referenceKind +
-//                ", referenceIndex=" + referenceIndex +
-//                '}';
-//    }
-//}
-
-//TODO implement later
\ No newline at end of file
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/MethodRefEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/MethodRefEntry.java
deleted file mode 100644
index f46eade..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/MethodRefEntry.java
+++ /dev/null
@@ -1,21 +0,0 @@
-package nl.sander.beejava.constantpool.entry;
-
-public class MethodRefEntry extends ConstantPoolEntry {
-    private final ClassEntry classEntry;
-    private final NameAndTypeEntry nameAndTypeEntry;
-
-    public MethodRefEntry(ClassEntry classEntry, NameAndTypeEntry nameAndTypeEntry) {
-        super(classEntry,nameAndTypeEntry);
-        this.classEntry = classEntry;
-        this.nameAndTypeEntry = nameAndTypeEntry;
-    }
-
-    public int getClassIndex() {
-        return classEntry.getIndex();
-    }
-
-    public int getNameAndTypeIndex() {
-        return nameAndTypeEntry.getIndex();
-    }
-
-}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/MethodTypeEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/MethodTypeEntry.java
deleted file mode 100644
index 420a146..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/MethodTypeEntry.java
+++ /dev/null
@@ -1,18 +0,0 @@
-//package nl.sander.beejava.constantpool.entry;
-//
-//public class MethodTypeEntry extends ConstantPoolEntry {
-//    private final int descriptorIndex;
-//
-//    public MethodTypeEntry(int descriptorIndex) {
-//        this.descriptorIndex = descriptorIndex;
-//    }
-//
-//    @Override
-//    public String toString() {
-//        return "MethodTypeEntry{" +
-//                "descriptorIndex=" + descriptorIndex +
-//                '}';
-//    }
-//}
-
-//TODO implement when I know that this is
\ No newline at end of file
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/ModuleEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/ModuleEntry.java
deleted file mode 100644
index 7440784..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/ModuleEntry.java
+++ /dev/null
@@ -1,11 +0,0 @@
-package nl.sander.beejava.constantpool.entry;
-
-public class ModuleEntry extends ConstantPoolEntry {
-
-    private final Utf8Entry nameEntry;
-
-    public ModuleEntry(Utf8Entry nameEntry) {
-        super(nameEntry);
-        this.nameEntry = nameEntry;
-    }
-}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/NodeConstant.java b/src/main/java/nl/sander/beejava/constantpool/entry/NodeConstant.java
new file mode 100644
index 0000000..23c39e8
--- /dev/null
+++ b/src/main/java/nl/sander/beejava/constantpool/entry/NodeConstant.java
@@ -0,0 +1,35 @@
+package nl.sander.beejava.constantpool.entry;
+
+import java.util.Arrays;
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+public abstract class NodeConstant {
+    protected final Set<NodeConstant> children; // TODO decide whether or not to keep this. Could also make getChildren abstract and make it return a new list every time
+                                                     // TODO to save storage. getChildren should only be called once, so it is probably more efficient like that
+    private int index; // the index of the entry is not known until after creation of the complete tree, so cannot be final, but it should not be updated.
+
+    protected NodeConstant(NodeConstant... children) {
+        this.children = new LinkedHashSet<>();
+        this.children.addAll(Arrays.asList(children)); // java8 way destroys order, not desastrous, but I like to preserve it.
+    }
+
+    /*
+     * The tag that indicates the entry type in the bytecode.
+     * §4.4 Table 4.4-A. Constant pool tags
+     */
+    public abstract int getTag();
+
+    public int getIndex() {
+        return index;
+    }
+
+    public void setIndex(int index) {
+        this.index = index;
+    }
+
+    public Set<NodeConstant> getChildren() {
+        return children;
+    }
+
+}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/PackageEntry.java b/src/main/java/nl/sander/beejava/constantpool/entry/PackageEntry.java
deleted file mode 100644
index aabe432..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/PackageEntry.java
+++ /dev/null
@@ -1,14 +0,0 @@
-package nl.sander.beejava.constantpool.entry;
-
-public class PackageEntry extends ConstantPoolEntry {
-    private final Utf8Entry name;
-
-    public PackageEntry(Utf8Entry name) {
-        super(name);
-        this.name = name;
-    }
-
-    public int getNameIndex() {
-        return name.getIndex();
-    }
-}
diff --git a/src/main/java/nl/sander/beejava/constantpool/entry/Utf8Entry.java b/src/main/java/nl/sander/beejava/constantpool/entry/Utf8Entry.java
deleted file mode 100644
index ffa2ad2..0000000
--- a/src/main/java/nl/sander/beejava/constantpool/entry/Utf8Entry.java
+++ /dev/null
@@ -1,20 +0,0 @@
-package nl.sander.beejava.constantpool.entry;
-
-public class Utf8Entry extends LeafEntry {
-    private final String stringVal;
-
-    public Utf8Entry(String utf8) {
-        this.stringVal = utf8;
-    }
-
-    public String getUtf8() {
-        return stringVal;
-    }
-
-    @Override
-    public String toString() {
-        return "Utf8Entry{" +
-                "stringVal='" + stringVal + '\'' +
-                '}';
-    }
-}
diff --git a/src/test/java/nl/sander/beejava/ConstantTreeCreatorTests.java b/src/test/java/nl/sander/beejava/ConstantTreeCreatorTests.java
index b67ceb1..d09ed0f 100644
--- a/src/test/java/nl/sander/beejava/ConstantTreeCreatorTests.java
+++ b/src/test/java/nl/sander/beejava/ConstantTreeCreatorTests.java
@@ -20,45 +20,45 @@ public class ConstantTreeCreatorTests {
     @Test // This is not a maintainable test
     public void testMethodRefEntryForSuperConstructor() {
         BeeClass classWithIntField = createEmptyClass();
-        Set<ConstantPoolEntry> constantTree = new ConstantTreeCreator().createConstantTree(classWithIntField);
+        Set<NodeConstant> constantTree = new ConstantTreeCreator().createConstantTree(classWithIntField);
         assertEquals(1, constantTree.size());
-        ConstantPoolEntry superConstructor = constantTree.iterator().next();
+        NodeConstant superConstructor = constantTree.iterator().next();
 
-        assertEquals(MethodRefEntry.class, superConstructor.getClass());
-        MethodRefEntry methodRefEntry = (MethodRefEntry) superConstructor;
+        assertEquals(ConstantMethodRef.class, superConstructor.getClass());
+        ConstantMethodRef constantMethodRef = (ConstantMethodRef) superConstructor;
 
-        Set<ConstantPoolEntry> methodRefEntryChildren = methodRefEntry.getChildren();
+        Set<NodeConstant> methodRefEntryChildren = constantMethodRef.getChildren();
         assertEquals(2, methodRefEntryChildren.size());
 
-        Iterator<ConstantPoolEntry> firstChildren = methodRefEntryChildren.iterator();
-        ConstantPoolEntry child1 = firstChildren.next();
-        assertEquals(ClassEntry.class, child1.getClass());
-        ClassEntry classEntry = (ClassEntry) child1;
+        Iterator<NodeConstant> firstChildren = methodRefEntryChildren.iterator();
+        NodeConstant child1 = firstChildren.next();
+        assertEquals(ConstantClass.class, child1.getClass());
+        ConstantClass constantClass = (ConstantClass) child1;
 
-        Set<ConstantPoolEntry> classEntryChildren = classEntry.getChildren();
+        Set<NodeConstant> classEntryChildren = constantClass.getChildren();
         assertEquals(1, classEntryChildren.size());
-        ConstantPoolEntry child2 = classEntryChildren.iterator().next();
+        NodeConstant child2 = classEntryChildren.iterator().next();
 
-        assertEquals(Utf8Entry.class, child2.getClass());
-        Utf8Entry className = (Utf8Entry) child2;
+        assertEquals(ConstantUtf8.class, child2.getClass());
+        ConstantUtf8 className = (ConstantUtf8) child2;
         assertEquals("java/lang/Object", className.getUtf8());
 
-        ConstantPoolEntry child3 = firstChildren.next();
-        assertEquals(NameAndTypeEntry.class, child3.getClass());
-        NameAndTypeEntry nameAndTypeEntry = (NameAndTypeEntry) child3;
+        NodeConstant child3 = firstChildren.next();
+        assertEquals(ConstantNameAndType.class, child3.getClass());
+        ConstantNameAndType constantNameAndType = (ConstantNameAndType) child3;
 
-        Set<ConstantPoolEntry> nameAndTypeEntryChildren = nameAndTypeEntry.getChildren();
+        Set<NodeConstant> nameAndTypeEntryChildren = constantNameAndType.getChildren();
         assertEquals(2, nameAndTypeEntryChildren.size());
-        Iterator<ConstantPoolEntry> nameAndTypeChildrenIterator = nameAndTypeEntryChildren.iterator();
+        Iterator<NodeConstant> nameAndTypeChildrenIterator = nameAndTypeEntryChildren.iterator();
 
-        ConstantPoolEntry child4 = nameAndTypeChildrenIterator.next();
-        assertEquals(Utf8Entry.class, child4.getClass());
-        Utf8Entry name = (Utf8Entry) child4;
+        NodeConstant child4 = nameAndTypeChildrenIterator.next();
+        assertEquals(ConstantUtf8.class, child4.getClass());
+        ConstantUtf8 name = (ConstantUtf8) child4;
         assertEquals("<init>", name.getUtf8());
 
-        ConstantPoolEntry child5 = nameAndTypeChildrenIterator.next();
-        assertEquals(Utf8Entry.class, child5.getClass());
-        Utf8Entry type = (Utf8Entry) child5;
+        NodeConstant child5 = nameAndTypeChildrenIterator.next();
+        assertEquals(ConstantUtf8.class, child5.getClass());
+        ConstantUtf8 type = (ConstantUtf8) child5;
         assertEquals("()V", type.getUtf8());
     }
 
diff --git a/src/test/java/nl/sander/beejava/constantpool/entry/TagCorrectnessTest.java b/src/test/java/nl/sander/beejava/constantpool/entry/TagCorrectnessTest.java
new file mode 100644
index 0000000..c917317
--- /dev/null
+++ b/src/test/java/nl/sander/beejava/constantpool/entry/TagCorrectnessTest.java
@@ -0,0 +1,49 @@
+package nl.sander.beejava.constantpool.entry;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * make sure tags were put in the code according to spec (§4.4)
+ */
+public class TagCorrectnessTest {
+    @Test
+    public void testSpec() {
+        assertEquals(7, classEntry().getTag());
+        assertEquals(9, fieldRef().getTag());
+        assertEquals(10, new ConstantMethodRef(classEntry(), nameAndType()).getTag());
+        assertEquals(11, new ConstantInterfaceMethodRef(classEntry(), nameAndType()).getTag());
+        assertEquals(8, new ConstantString(utf8()).getTag());
+        assertEquals(3, new ConstantInteger(0).getTag());
+        assertEquals(4, new ConstantFloat(0).getTag());
+        assertEquals(5, new ConstantLong(0).getTag());
+        assertEquals(6, new ConstantDouble(0).getTag());
+        assertEquals(12, nameAndType().getTag());
+        assertEquals(1, utf8().getTag());
+        assertEquals(15, new ConstantMethodHandle(0).getTag()); //TODO
+        assertEquals(16, new ConstantMethodType(utf8()).getTag()); //TODO
+        assertEquals(17, new ConstantDynamic(0, nameAndType()).getTag()); //TODO
+        assertEquals(18, new ConstantInvokeDynamic(0, nameAndType()).getTag()); //TODO
+        assertEquals(19, new ConstantModule(utf8()).getTag());
+        assertEquals(20, new ConstantPackage(utf8()).getTag());
+
+    }
+
+    private ConstantFieldRef fieldRef() {
+        return new ConstantFieldRef(classEntry(), nameAndType());
+    }
+
+    private ConstantNameAndType nameAndType() {
+        return new ConstantNameAndType(utf8(), utf8());
+    }
+
+
+    private ConstantClass classEntry() {
+        return new ConstantClass(utf8());
+    }
+
+    private ConstantUtf8 utf8() {
+        return new ConstantUtf8("");
+    }
+}