集合的遍历

List 的遍历

ArrayList<String> list = new ArrayList<>();

===1 forEach循环遍历===
	list.forEach(new Consumer<String>() {
        @Override
        public void accept(String s) {
            System.out.println(s);
         }
    });

	// JDK8开始 出现lambda表达式 新语法
    list.forEach((s) -> {
    	System.out.println(s);
	});

===2 增强for循环遍历===
	System.out.println();
        for (String s : list) {
            System.out.println(s);
        }
====3 迭代器遍历======
	System.out.println();
        Iterator<String> iterator = list.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }

Set的遍历

Set<String> set1 = new HashSet<>();
==1增强for遍历==
        for (String s : set1) {
            System.out.println(s);
        }

==2 迭代器遍历==
        Iterator<String> iterator = set1.iterator();
        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }

==3 forEach 匿名内部类==
        set1.forEach(new Consumer<String>() {
            @Override
            public void accept(String s) {
                System.out.println(s);
            }
        });
==3 lambda表达式==
        set1.forEach((a) -> {
            System.out.println(a);
        });

Map的遍历

 Map<Integer, String> map = new HashMap<>();
        
==1 先获取所有的Key对象,再依次根据Key对象取对应的value对象==
        Set<Integer> keySet = map.keySet();
        for (Integer key : keySet) {
            System.out.println(key + "=" + map.get(key));
        }

==2 forEach==
        map.forEach(new BiConsumer<Integer, String>() {
            @Override
            public void accept(Integer key, String value) {
                System.out.println(key + "=" + value);
            }
        });

==2 lambda表示==
        map.forEach((k, v) -> {
            System.out.println(k + "=" + v);
        });

==3 entrySet集合遍历==
        Set<Map.Entry<Integer, String>> entrySet = map.entrySet();
        for (Map.Entry<Integer, String> entry : entrySet) {
            System.out.println(entry.getKey() + "=" + entry.getValue());
        }