Java8's six new features fourth method reference and constructor call

lamdba expressions can be simplified

The following introduces 6 ways to simplify lamdba, also known as method or constructor reference.

If a lambda expression represents just calling this method directly, it is better to call it by name instead of describing how to call it. Explicitly specifying the name of the method can make your code more readable.

1. The parameter category and return type must be consistent with the abstract method in the functional interface.
2. If the first parameter in the parameter list is the caller of the instance method and the second parameter is the parameter of the instance method, you can use ClassName: :method

Object::instance method - method reference

    //用lambda表达式实现
    Consumer consumer = x -> System.out.println(x);
    consumer.accept("hello world");
    //out实现了println方法
    Consumer consumer1 =System.out::println;
    consumer1.accept("hello word 1");

Class name:: static method - method reference

    //用lambda表达式实现
    BiFunction<Integer, Integer, Integer> biFun = (x,y) -> Integer.compare(x,y);
    //类名：：静态方法
    BiFunction<Integer, Integer, Integer> biFun1 = Integer::compare;
    int result1 = biFun.apply(100,200);
    int result2 = biFun1.apply(100,200);

Class name::instance method - method reference

    //用lambda表达式实现
    BiFunction<String,String,Boolean> fun1 = (s1,s2)-> s1.equals(s2);
    //类名：：实例方法
    BiFunction<String,String,Boolean> fun2 = String::equals;
    fun1.apply("hello","hello");
    fun2.apply("hello","hello");

Class name::new - constructor reference

    //用lambda表达式实现
    Supplier<String> sup = ()->new String();
    //构造方法引用 类名：：new
    Supplier<String> sup1 = String::new;

Class name::new() - constructor reference

    //用lambda表达式实现
    Function<String,Integer> function = x->new Integer(x);
    //类名：：new
    Function<String,Integer> function1 = Integer::new;
    function1.apply("100");

String[]:::new --Array reference

    //用lambda表达式实现
    Function <Integer,String[]> array = x -> new String [x];
    //类型[]::new
    Function <Integer,String[]> array1 = String[]::new;
    array1.apply(5);

All code execution results:

No error

1000
10

Process finished with exit code 0