简单实现Set To Map_java

简单实现Set To Map （就那么不经意）

package cn.limbo.collection;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;

/**
* Created by lhh on 2017/12/13.
*/
public class SimpleEntry<K, V> implements Map.Entry<K, V>, java.io.Serializable {
private final K key;//key是唯一的不可变的
private V value;

public SimpleEntry(K key, V value) {
this.key = key;
this.value = value;
}

public SimpleEntry(Map.Entry<? extends K, ? extends V> entry) {
this.key = entry.getKey();
this.value = entry.getValue();
}

@Override
public K getKey() {//获取key
return key;
}

@Override
public V getValue() {
return value;
}

//改变key-value对应的value的值
@Override
public V setValue(V value) {
V oldValue = this.value;
this.value = value;
return oldValue;
}

//根据key判断value是否相等
public boolean equals(Object o) {
if (o == this) {
return true;
}
if (o.getClass() == SimpleEntry.class) {
SimpleEntry se = (SimpleEntry) o;
return se.getKey().equals(getKey());
}
return false;
}

//根据key计算对应的hashcode
public int hashCode() {
return key == null ? 0 : key.hashCode();
}

@Override
public String toString() {
return key + "=" + value;
}
}

class Set2Map<K, V> extends HashSet<SimpleEntr
4000
y<K, V>> {

public void clear() {
super.clear();
}

//判断是否包含某个key
public boolean containsKey(K key) {
return super.contains(
new SimpleEntry<K, V>(key, null));
}

//判断是否包含某个value
boolean containsValue(Object value) {
for (SimpleEntry<K, V> se : this) {
if (se.getValue().equals(value)) {
return true;
}
}
return false;
}

//根据指定key取出对应的value
public V get(Object key) {
for (SimpleEntry<K, V> se : this) {
if (se.getKey().equals(key)) {
return se.getValue();
}
}
return null;
}

//将指定的key-value放入到集合
public V put(K key, V value) {
add(new SimpleEntry<K, V>(key, value));
return value;
}

//将另一个Map的key-value放入到map
public void putAll(Map<? extends K, ? extends V> m) {
for (K key : m.keySet()) {
add(new SimpleEntry<K, V>(key, m.get(key)));
}
}

//根据key删除指定key-value对
public V removeEntry(Object key) {

for (Iterator<SimpleEntry<K, V>> it = this.iterator(); it.hasNext(); ) {
SimpleEntry<K, V> en = it.next();
if (en.getKey().equals(key)) {
V v = en.getValue();
it.remove();
return v;
}
}
return null;
}

//获取key-value对
public int size() {
return super.size();
}

}

//编写测试类
class Set2MapTest {
public static void main(String[] args) {
Set2Map<String, Integer> scores = new Set2Map<>();
//把key-value对放到该集合
scores.put("语文", 70);
scores.put("数学", 95);
scores.put("英语", 80);
System.out.println("scores = " + scores);
//访问Map
System.out.println("scores.get(\"语文\") = " + scores.get("语文"));
System.out.println(scores.size());
scores.removeEntry("数学");
System.out.println(scores.size());
System.out.println(scores.containsKey("数学"));
System.out.println(scores.containsValue(80));
scores.clear();
System.out.println("清除之后的map:[]scores = " + scores);
}
}