Duplicate Keys in Hashmap

Question

The following code and output illustrate the core of my prolems using HashMap. I've created a simple key class wrapping a string and implementing equals, hashcode and compareTo. Entries can only be accessied via iterators and duplicates appear. Using a TreeMap instead works fine, but I need the speed of hashmap for now.:
import java.util.*;
import java.io.*;
import java.awt.event.*;
import java.awt.*;
class GenericGraphKey implements Comparable{
private String val="";
public GenericGraphKey(String value){ val=value; }
public boolean equals(GenericGraphKey k){
System.out.println("equals()");
return val.equals(k.val);
public int hashCode() {
System.out.println("hashCode():"+val.hashCode());
return val.hashCode();
public int compareTo(Object o) {
System.out.println("compareTo()");
GenericGraphKey n=(GenericGraphKey)o;
return val.compareTo(n.val);
public String toString(){ return ("["+val+"]"); }
public class TestApp {
     public static void main(String[] args) {
HashMap t=new HashMap();
System.out.print("A:");
GenericGraphKey k1=new GenericGraphKey("John");
System.out.println("Put "+k1+",a :"+(String)t.put(k1,"a") );
System.out.print("B:");
GenericGraphKey k2=new GenericGraphKey("John");
System.out.println("Get "+k2+":"+(String)t.get(k2));
System.out.print("C:");
GenericGraphKey k3=new GenericGraphKey("John");
System.out.println("Put "+k3+",b :"+(String)t.put(k3,"b"));
System.out.print("D:");
GenericGraphKey k4=new GenericGraphKey("John");
System.out.println("Get "+k4+":"+(String)t.get(k4));
System.out.print("E:");
GenericGraphKey k5=new GenericGraphKey("Jane");
System.out.println("Put "+k5+",c :"+(String)t.put(k5,"c"));
System.out.print("F:");
GenericGraphKey k6=new GenericGraphKey("Jane");
System.out.println("Get "+k6+":"+(String)t.get(k6));
System.out.print("G:");
GenericGraphKey k7=new GenericGraphKey("Allan");
System.out.println("Put "+k7+",d :"+(String)t.put(k7,"d"));
System.out.print("H:");
GenericGraphKey k8=new GenericGraphKey("Allan");
System.out.println("Put "+k8+",e :"+(String)t.put(k8,"e"));
System.out.print("I:");
GenericGraphKey k9=new GenericGraphKey("Allan");
System.out.println("Get "+k9+":"+(String)t.get(k9));
System.out.println();
Map.Entry e=null;
for (Iterator i=t.entrySet().iterator(); i.hasNext();){
e = (Map.Entry) i.next();
System.out.print("{"+(String)e.getValue()+"}");
System.out.println();
System.out.println(t.keySet());
Output:
A:hashCode():2314539
Put [John],a :null
B:hashCode():2314539
Get [John]:null
C:hashCode():2314539
Put [John],b :null
D:hashCode():2314539
Get [John]:null
E:hashCode():2301262
Put [Jane],c :null
F:hashCode():2301262
Get [Jane]:null
G:hashCode():63353198
Put [Allan],d :null
H:hashCode():63353198
Put [Allan],e :null
I:hashCode():63353198
Get [Allan]:null
{c}{e}{d}{b}{a}
[[Jane], [Allan], [Allan], [John], [John]]
Thanks to anyone who can get things moving on again.

Answer 1

Hombre below is an illustration of what Chrisboy and jverd are telling you.
If the parent class has a method with the same signature as one in an interface which the child class implements then your IDE and javac will not say anything about you not haveing implemented the class in the interface.
The following code compiles and at least Netbeans also has no problems with it.
public class NewClass
    public NewClass()
    public void someMethod()
public interface NewInterface
    public void someMethod();
public class NewClass2 extends NewClass implements NewInterface
    public NewClass2()
}