jdk1.8 新特性之 forEach 循环遍历

https://yq.aliyun.com/articles/44712

1、Foreach操作List

List numbers = new ArrayList<>();

//no.1
for(Integer number : numbers){
    System.out.println(number);
}

//no.2
for(int index=0,len=numbers.size();index

使用jdk1.8后，可这么写

//no.1
numbers.forEach((Integer integer) -> {
    System.out.println(integer);
});

//no.2
numbers.forEach(integer -> {
    System.out.println(integer);
});

//no.3
numbers.forEach(integer -> System.out.println(integer));

//no.4
numbers.forEach(System.out::println);

//no.5
numbers.forEach(new MyConsumer());

2、 Foreach操作Map

1.1 正常方式遍历Map

Map<String, Integer> items = new HashMap<>();
items.put("A", 10);
items.put("B", 20);
items.put("C", 30);
items.put("D", 40);
items.put("E", 50);
items.put("F", 60);

for (Map.Entry<String, Integer> entry : items.entrySet()) {
    System.out.println("Item : " + entry.getKey() + " Count : " + entry.getValue());
}

1.2 使用Java8的foreach+lambda表达式遍历Map

Map<String, Integer> items = new HashMap<>();
items.put("A", 10);
items.put("B", 20);
items.put("C", 30);
items.put("D", 40);
items.put("E", 50);
items.put("F", 60);

items.forEach((k,v)->System.out.println("Item : " + k + " Count : " + v));

items.forEach((k,v)->{
    System.out.println("Item : " + k + " Count : " + v);
    if("E".equals(k)){
        System.out.println("Hello E");
    }
});

###2. Foreach操作List
2.1 普通方式循环List

List<String> items = new ArrayList<>();
items.add("A");
items.add("B");
items.add("C");
items.add("D");
items.add("E");

for(String item : items){
    System.out.println(item);
}

2.2 在Java8中使用foreach+lambda表达式遍历List

List<String> items = new ArrayList<>();
items.add("A");
items.add("B");
items.add("C");
items.add("D");
items.add("E");

//lambda
//Output : A,B,C,D,E
items.forEach(item->System.out.println(item));
    
//Output : C
items.forEach(item->{
    if("C".equals(item)){
        System.out.println(item);
    }
});
    
//method reference
//Output : A,B,C,D,E
items.forEach(System.out::println);

//Steam and filter
//Output : B
items.stream()
    .filter(s->s.contains("B"))
    .forEach(System.out::println);