Java面向对象程序设计

课后作业：在Map中，还提供了一个values()方法，通过这个方法可以直接获取Map中存储所有值的Collection集合。请采用集合遍历的方式完成。（ 参考：通过遍历Map集合中所有的键，获取相应的值的方式。）

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package com.pujunming.nsusoft.Unit4.fanxing;

/**
 * Created by Intellij IDEA.
 *
 * @author Pu_Junming
 * @create 2022/11/29 16:36
 */

class Box<K,V>{
    private K key;
    private V value;

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

    public K getKey() {
        return key;
    }

    public void setKey(K key) {
        this.key = key;
    }

    public V getValue() {
        return value;
    }

    public void setValue(V value) {
        this.value = value;
    }
}

public class Demo001 {
    public static void main(String[] args){
        Box<String,String> c1 = new Box<String,String>("name", "puJunMing");
        Box<String,Integer> c2 = new Box<String, Integer>("age", 22);
        Box<Double,Double> c3 = new Box<Double, Double>(22.1,22.1);
        System.out.println(c1.getKey() + "=" + c1.getValue());
        System.out.println(c2.getKey() + "=" + c2.getValue());
        System.out.println(c3.getKey() + "=" + c3.getValue());
    }
}

通过一个案例来演示先遍历Map集合中所有的键，再根据键获取相应的值的方式。

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import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class Dome2 {
    public static void main(String[] args) {
        Map map=new HashMap (  );
        map.put ( "1","Jack" );
        map.put ( "2","Tom" );
        map.put ( "3","luck" );
        Set keyset=map.keySet () ;
        Iterator it=keyset.iterator ();
        while (it.hasNext ()){
            Object key=it.next ();
            Object value=map.get ( key );
            System.out.println ( key+":"+value );
        }
    }
}

定义泛型方法：通过一个自定义的比较方法compare(pN,pM),完成对不同的实例对象pN和pM的比较。

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package com.pujunming.nsusoft.Unit4.fanxing;

import static java.util.Arrays.compare;

/**
 * Created by Intellij IDEA.
 *
 * @author Pu_Junming
 * @create 2022/11/29 16:36
 */

class Pair<K,V>{
    private K key;
    private V value;

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

    public K getKey() {
        return key;
    }

    public void setKey(K key) {
        this.key = key;
    }

    public V getValue() {
        return value;
    }

    public void setValue(V value) {
        this.value = value;
    }
}

public class Demo002 {
    public static void main(String[] args){
        Pair<String,String> p1 = new Pair<String,String>("name", "pu");
        Pair<String,String> p2 = new Pair<String,String>("name", "huang");
        System.out.println("比较结果：p1 = p2\t" + compare(p1, p2));

        Pair<String,Integer> p3 = new Pair<String,Integer>("age", 22);
        Pair<String,Integer> p4 = new Pair<String,Integer>("age", 22);
        System.out.println("比较结果：p3 = p4\t" + compare(p3, p4));
    }
    public static <K,V> boolean compare(Pair<K,V> pp,Pair<K,V> tt){
        return pp.getKey ().equals ( tt.getKey () )&&
                pp.getValue ().equals ( tt.getValue () );
    }
}