让星星⭐月亮告诉你，jdk1.8 Java函数式编程示例:Lambda函数/方法引用/4种内建函数式接口(功能性-/消费型/供给型/断言型)

package unittest;

import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.Supplier;

@FunctionalInterface
interface IFuction1

{
public abstract P uppCase();
}
@FunctionalInterface
interface IFuction2

{
public abstract P uppCase(P p);
}
@FunctionalInterface
interface IFuction3{
public abstract R trans(P p);
}
public class TestLocal{
public static void main(String[] args) {
//利用方法引用的概念可以位一个方法定义多个名字,但是要求必须是函数式接口.

    IFuction1<String> ifunction1  = "avc" :: toUpperCase;//    public String toUpperCase() {
    String str1 = ifunction1.uppCase();//实例对象::普通方法(不带参数)
    System.out.println(str1);

    IFuction2<String> ifunction2  = String :: toUpperCase; //    public String toUpperCase() {
    String str2 = ifunction2.uppCase("avc");//类名称::普通方法(带参数)
    System.out.println(str2);

    IFuction3<Integer,String> ifunction3  = String :: valueOf;//类名称::static方法(带参数) //    public static String valueOf(int i) {
    String str3 = ifunction3.trans(123456);
    System.out.println(str3.length());
    //内建函数式接口
    //1.功能型内建函数式接口:有参数 有返回值
    Function<String,Boolean> fun = "abc123"::startsWith;
    System.out.println("1功能型内建函数式接口:" + fun.apply("abc"));

    //2.消费型内建函数式接口:有参数 无返回值
    Consumer<String> con = System.out::println;
    con.accept("2消费型内建函数式接口:avc");
    //3.供给型内建函数式接口:无参数 有返回值
    Supplier<String> supplier = "abc"::toUpperCase;
    System.out.println("3供给型内建函数式接口:" + supplier.get());
    //4.断言型内建函数式接口:无参数 有返回值
    Predicate<String> predicate = String::isEmpty;
    System.out.println("4断言型内建函数式接口:" + predicate.test("a"));

    Predicate<String> fun_predicate = "abc123"::startsWith;
    System.out.println("5功能_断言型内建函数式接口:" + fun_predicate.test("abc"));
}

}