JAVA8之方法引用和構造引用
阿新 • • 發佈:2019-01-29
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);
}
這裡的2和3有點繞,主要區別在於例項一個為引數一個為外部物件.
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);
}