hash-B-使用在哈希法存储数据

package i_hash.B_hashDouble;


import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


/**
 * 使用在哈希法存储数据
 * 
 * @author Administrator
 * 
 */
public class HashDoubleApp {
public static void main(String[] args) throws NumberFormatException,
IOException {
int size, n, aKey;
DataItem aDataItem;
System.out.print("请指定哈希表的大小: ");
size = getInt();
System.out.print("指定哈希表初始化数据量：");
n = getInt();
HashTable theHashTable = new HashTable(size);
for (int i = 0; i < n; i++) {
aKey = (int) (Math.random() * 2 * size);
aDataItem = new DataItem(aKey);
theHashTable.insert(aKey, aDataItem);
}
while (true) {
System.out.print("请输入第一个字母：");
System.out.println("find,insert,show or delete");
char choice = getChar();
switch (choice) {
case 'i':
System.out.print("请输入要插入的值: ");
aKey = getInt();
aDataItem = new DataItem(aKey);
theHashTable.insert(aKey, aDataItem);
break;
case 's':
theHashTable.display();
break;
case 'f':
System.out.print("请输入要查询的值: ");
aKey = getInt();
aDataItem = theHashTable.find(aKey);
if (aDataItem != null) {
System.out.println("找到值：" + aKey);
} else {
System.out.println("没有找到值：" + aKey);
}
break;
case 'd':
System.out.println("请输入要删除的值：");
aKey = getInt();
theHashTable.delete(aKey);
break;


default:
System.out.println("无效输入！！！");
}


}
}


private static char getChar() throws IOException {
return getString().charAt(0);
}


private static String getString() throws IOException {
return new BufferedReader(new InputStreamReader(System.in)).readLine();
}


private static int getInt() throws NumberFormatException, IOException {
return Integer.parseInt(getString());
}
}package i_hash.B_hashDouble;


public class HashTable {
private DataItem[] hashArray;
private int arraySize;
private DataItem nonItem;


public HashTable(int size) {
arraySize = size;
hashArray = new DataItem[arraySize];
nonItem = new DataItem(-1);
}


public void display() {
System.out.print("Table: ");
for (int i = 0; i < arraySize; i++) {
if (hashArray[i] != null) {
System.out.print(hashArray[i].getKey() + " ");
} else {
System.out.print("** ");
}
}
System.out.println();
}


private int hashFunc1(int key) {
return key % arraySize;
}


private int hashFunc2(int key) {
return 5 - key % 5;
}


public void insert(int key, DataItem item) {
int hashVal = hashFunc1(key);
int stepSize = hashFunc2(key);
while (hashArray[hashVal] != null && hashArray[hashVal].getKey() != -1) {
hashVal += stepSize;
hashVal %= arraySize;
}
hashArray[hashVal] = item;
}


public DataItem delete(int key) {
int hashVal = hashFunc1(key);
int stepSize = hashFunc2(key);
while (hashArray[hashVal] != null) {
if (hashArray[hashVal].getKey() == key) {
DataItem temp = hashArray[hashVal];
hashArray[hashVal] = nonItem;
return temp;
}
hashVal += stepSize;
hashVal %= arraySize;
}
return null;
}


public DataItem find(int key) {
int hashVal = hashFunc1(key);
int stepSize = hashFunc2(key);
while (hashArray[hashVal] != null) {
if (hashArray[hashVal].getKey() == key) {
return hashArray[hashVal];
}
hashVal += stepSize;
hashVal %= arraySize;
}
return null;
}
}package i_hash.B_hashDouble;


public class DataItem {
private int iData;


public DataItem(int iData) {
super();
this.iData = iData;
}

public int getKey(){
return iData;
}


}