Interestingly, % in Java or C doesn't give the results that the modulo is

mathematically defined to...it can return negative numbers...

diff --git a/Robust/src/ClassLibrary/HashMap.java b/Robust/src/ClassLibrary/HashMap.java
index d977e0527443c957188a0136455f4cc85c82e8ae..11dfdf3f5fef477efeae57f3230d9576618af839 100644 (file)
--- a/Robust/src/ClassLibrary/HashMap.java
+++ b/Robust/src/ClassLibrary/HashMap.java
@@ -21,20 +21,30 @@ public class HashMap {
        this.numItems=0;
     }
 
+    private int hash(Object o) {
+       if (o==null)
+           return 0;
+       int value=o.hashCode()%table.length;
+       if (value<0)
+           return -value;
+       return value;
+    }
+
     void resize() {
        int newCapacity=2*table.length+1;
-       HashEntry[] newtable=new HashEntry[newCapacity];
-       for(int i=0;i<table.length;i++) {
-           HashEntry e=table[i];
+       HashEntry[] oldtable=table;     
+       this.table=new HashEntry[newCapacity];
+
+       for(int i=0;i<oldtable.length;i++) {
+           HashEntry e=oldtable[i];
            while(e!=null) {
                HashEntry next=e.next;
-               int bin=e.key.hashCode()%newCapacity;
-               e.next=newtable[bin];
-               newtable[bin]=e;
+               int bin=hash(e.key);
+               e.next=table[bin];
+               table[bin]=e;
                e=next;
            }
        }
-       this.table=newtable;
     }
 
     public boolean isEmpty() {
@@ -51,7 +61,7 @@ public class HashMap {
     }
 
     Object remove(Object key) {
-       int bin=key.hashCode()%table.length;
+       int bin=hash(key);
        HashEntry ptr=table[bin];
        if (ptr.key.equals(key)) {
            table[bin]=ptr.next;
@@ -71,7 +81,7 @@ public class HashMap {
     }
 
     Object get(Object key) {
-       int bin=key.hashCode()%table.length;
+       int bin=hash(key);
        HashEntry ptr=table[bin];
        while(ptr!=null) {
            if (ptr.key.equals(key)) {
@@ -83,7 +93,7 @@ public class HashMap {
     }
 
     boolean containsKey(Object key) {
-       int bin=key.hashCode()%table.length;
+       int bin=hash(key);
        HashEntry ptr=table[bin];
        while(ptr!=null) {
            if (ptr.key.equals(key)) {
@@ -100,7 +110,7 @@ public class HashMap {
            //Resize the table
            resize();
        }
-       int bin=key.hashCode()%table.length;
+       int bin=hash(key);
        HashEntry ptr=table[bin];
        while(ptr!=null) {
            if (ptr.key.equals(key)) {