其實關於方法引用和構造引用大家可以簡單理解為lambda的簡寫形式

一.方法引用

方法引用分為三類:

1.指向靜態方法的方法引用

例子:

public static void main(String[] args) {
		String num="122";
		int parse = parse(Integer::parseInt,num);
		System.out.println(parse);
	}
	public static int parse(ToIntFunction<String> f,String num){
		return f.applyAsInt(num);
	}
 

2.指向任意型別例項方法的方法引用(這個例項長為方法的引數)

例子:

public static void main(String[] args) {
		List<String> list = Arrays.asList("av","asdf","sad","324","43");
		List<String> collect = list.stream().map(String::toUpperCase).collect(Collectors.toList());
		System.out.println(collect);
	}

3.指向現有物件的例項方法的方法引用(這個例項為外部物件)

例子:

public static void main(String[] args) {
		List<String> list = Arrays.asList("av","asdf","sad","324","43");
		String a="avasdf";
		List<String> collect = list.stream().filter(a::contains).collect(Collectors.toList());
		System.out.println(collect);
	}

二:構造引用

	private String color;
	private int weight;
	public Apple() {
	}
	
	public Apple(String color) {
		super();
		this.color = color;
	}

	public Apple(int weight) {
		super();
		this.weight = weight;
	}

	public Apple(String color, int weight) {
		super();
		this.color = color;
		this.weight = weight;
	}

	@Override
	public String toString() {
		return "Apple [color=" + color + ", weight=" + weight + "]";
	}

public static void main(String[] args) {
		Apple instance1 = instance(11,Apple::new);
	}
	public static Apple instance(int a,IntFunction<Apple> ifu){
		return ifu.apply(a);
	}