關於hash衝突的解決

分離連結法：
public class SeparateChainingHashTable<AnyType>{
private static final int DEFAULT_TABLE_SIZE=101;
private List<AnyType> []theLists;
private int currentSize;

public SeparateChainingHashTable()
{this(DEFAULT_TABLE_SIZE);}

public SeparateChainingHashTable(int size){
theLists=new LinkedList[nextPrime(size)];
for(int i=0;i<theLists.length;i++)
theLists[i]=new LinkedList<AnyType>();
}

public void makeEmpty(){
for(int i=0;i<theLists.length;i++)
theList[i].clear();
current=0;
}

public boolean contains(AnyType x){
List<AnyType> whichList=theLists[myhash(x)];
return whichList.contains(x);
}

public void insert(AnyType x){
List<AnyType> whichList=theLists[myhash(x)];
if(!whichList.contains(x)){
whichList.add(x);
if(++currentSize>theLists.length)
rehash();
}
}

public void remove(AnyType x){
List<AnyType> whichList=theLists[myhash(x)];
if(whichList.contains(x)){
whichList.remove(x);
currentSize--;
}
}

public void rehash(){
List<AnyType> [] oldLists=theLists;
theList=new List[nextPrime(2*theList.length)];
for(int j=0;i<theList.length;j++)
theList[i]=new LinkedList<AnyType>();
currentSize=0;
for(int i=0;i<oldLists.length;i++)
for(AnyType item:oldLists[i])
insert(item);
//這裡呼叫的自己寫的類的insert方法，而不是對oldList物件進行add
}
}

public int myhash(AnyType x){
int hashVal=x.hashCode();
hashVal=hashVal%theLists.length;
if(hashVal<0)
hashVal=hashVal+theLists.length;
return hashVal;
}
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平方探測：

public class QuadraticProbingHashTable<AnyType>{
private static final int DEFAULT_TABLE_SIZE=11;
private HashEntry<AnyType> [] array;
private int currentSize;

public static class HashEntry<AnyType>{
public AnyType element;
public boolean isActive;
public HashEntry(AnyType e)
{this(e,true);}
public HashEntry(AnyType e,boolean i)
{element=e;isActive=i;}
}

public QuadraticProbingHashTable()
{this(DEFAULT_TABLE_SIZE);}

public QuadraticProbingHashTable(int size)
{allocateArray(size);makeEmpty();}

public void allocateArray(int arraysize)
{array=new HashEntry(arraysize);}

public void makeEmpty(){
currentSize=0;
for(int i=0;i<array.length;i++)
array[i]=null;
}

public boolean contains(AnyType x){
int currentPos=findPos(x);
return isActive(currentPos);
}

public int findPos(AnyType x){
int offset=1;
int currentPos=myhash(x);
//使用平方探測法進行雜湊
while(array[currentPos]!=null&&
!array[currentPos].element.equal(x)){
currentPos=currentPos+offset;
offset=offset+2;
if(currentPos>array.length)
currentPos=currentPos-array.length;
}
return currentPos;
}

public boolean isActive(int currentPos){
return array[currentPos]!=null&&
array[currentPos].isActive;
}

public void insert(AnyType x){
int currentPos=findPos(x);
if(isActive(currentPos))
return;
array[currentPos]=new HashEntry<AnyType>(x,true);
if(++currentSize>array.length/2)
rehash();
}

private void rehash(){
HashEntry<AnyType> []oldArray=array;
allocateArray(nextPrime(2*oldArray.length))
currentSize=0;
for(int i=0;i<oldArray.length;i++)
if(oldArray[i]!=null&&oldArray[i].isActive)
insert(oldArray[i].element);
}

public void remove(AnyType x){
int currentPos=findPos(x);
if(isActive(currentPos))
array[currentPos].isActive=false;
}

}