Java: Method Reference

类名::引用实例方法
Java 类名只能引用静态方法, 类名引用实例方法是拿第一个参数作为方法的调用者

import java.util.function.BiFunction;
import java.util.function.Function;

public class addThen{
  public static void main(String[] args){
    Function<String, Integer> f1 = s -> s.length();
    System.out.println("f1.apply(\"etymology\") = " + f1.apply("etymology"));

    Function<String, Integer> f2 = String::length;
    System.out.println("f2.apply(\"etymology\") = " + f2.apply("etymology"));

    BiFunction<String, Integer, String> biFunction = String::substring;
    System.out.println("biFunction.apply(\"etymology\",3) = " + biFunction.apply("etymology", 3));
  }
}

类名::new

import java.util.function.BiFunction;
import java.util.function.Supplier;

public class addThen{
  public static void main(String[] args){
    Supplier<Jot> supplier1 = Jot::new;
    System.out.println("supplier1 = " + supplier1.get());

    BiFunction<String,Integer,Jot> supplier2=Jot::new;
    System.out.println("\033[37;7m" + supplier2.apply("jot", 55) + "\033[0m");

  }
}

class Jot{
  String name;
  int age;

  @Override
  public String toString(){
    final StringBuilder sb = new StringBuilder("Jot{");
    sb.append("name='").append(name).append('\'');
    sb.append(", age=").append(age);
    sb.append('}');
    return sb.toString();
  }

  public Jot(){
  }

  public Jot(String name, int age){
    this.name = name;
    this.age = age;
  }
}

数组::new String[]::new

public class addThen{
  public static void main(String[] args){
    Function<Integer,String[]> f1=len->new String[len];
    String[] strings = f1.apply(5);
    System.out.println("strings = " + Arrays.toString(strings));

    Function<Integer,String[]>  f2=String[]::new;
    String[] strings1 = f2.apply(3);
    System.out.println("strings1 = " + Arrays.toString(strings1));
  }
}