Java-Map集合的学习

package com.ftl;

import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.TreeMap;

public class Test2018 {
    public static void main(String[] args) {

        Map<String, String> map = new TreeMap<>();
        map.put("Hello", "world");
        map.put("Hello1", "world1");
        map.put("Hello2", "world2");
        map.put("Hello3", "world3");
        String str = map.get("Hello");
        Set<String> set = map.keySet();
        Collection<String> values = map.values();
        Iterator<String> iterator = set.iterator();
        Iterator<String> iter = values.iterator();
        System.out.println("\nforeach方法：");
        for (String s : values) {
            System.out.print(s + "、");
        }
        System.out.println("\nIterator方法：");
        while (iterator.hasNext()) {
            System.out.print(iterator.next() + "、");
        }
        System.out.println("\nMap的标准输出_1(Map.entrySet)：");
        Set<Entry<String, String>> entrySet = map.entrySet();
        Iterator<Map.Entry<String, String>> it = entrySet.iterator();
        while (it.hasNext()) {
            Map.Entry<String, String> next = it.next();
            System.out.print(next.getKey() + "-->: " + next.getValue() + "\n");
        }
        System.out.println("\nMap的标准输出_2(Foreach)：");
        for (Map.Entry<String, String> entry : entrySet) {
            System.out.print(entry.getKey() + "-->: " + entry.getValue() + "\n");
        }
        System.out.println("Map.entrySet()大小：" + map.entrySet().size());
    }
}