92 java8新特性_3 _函数式接口函数式接口函数式接口：如果一个接口只有一个抽象方法，则该接口称之为函数式接口，函数式接口可以使用Lambda表达式，Lambda表达式会被匹配到这个抽象方法上。只有函数式接口才能使用lambda表达式@FunctionalInterface 注解检测接口是否符合函数式接口。
代码1：
package com.wlw.chapter13_java8.demo01;/** * 函数式接口 */@FunctionalInterface //检测接口是否符合函数式接口。public interface Usb { void service();}package com.wlw.chapter13_java8.demo01;public class Demo { public static void main(String[] args) { //匿名内部类 Usb mouse = new Usb() { @Override public void service() { System.out.println(“鼠标开始工作了…..”); } }; //lambda表达式 Usb fan = ()->{ System.out.println(“风扇开始工作了……..”); }; //Usb fan2 = ()-> System.out.println(“风扇开始工作了2……..”); run(mouse); run(fan); } public static void run(Usb usb){ usb.service(); }}/*执行结果:鼠标开始工作了…..风扇开始工作了……..*/常见的函数式接口
函数式接口
方法参数类型
方法返回类型
说明
Consumer< T>
消费型接口
T
void
void accept(T t); 对类型为T的对象应用操作
Supplier< T>
供给型接口
无
T
T get(); 返回类型为T的对象
Function<T,R>
函数型接口
T
R
R apply(T t); 对类型为T的对象应用操作，并返回类型为R类型的对象。
Predicate< T>
断言型接口
T
boolean
boolean test(T t); 确定类型为T的对象是否满足条件，并返回boolean类型。
代码1:
package com.wlw.chapter13_java8.demo01;import com.wlw.chapter9_thread.casedemo04.Consume;import java.util.Arrays;import java.util.Random;import java.util.function.Consumer;import java.util.function.Supplier;public class Demo { public static void main(String[] args) { //匿名内部类 Consumer<Double> consumer = new Consumer<Double>() { @Override public void accept(Double money) { System.out.println(“consumer唱歌消费了:”+money); } }; //lambda表达式 ,如果形参只有1个，()可以省略，只需要参数的名称即可， Consumer<Double> consumer1 = t ->{ System.out.println(“consumer1唱歌消费了:”+ t); }; happy(consumer,1000.0); happy(consumer1,1000.1); happy(t-> System.out.println(“consumer3吃饭消费了:”+ t),2000.0); System.out.println(“=====================================================================”); //匿名内部类 Supplier<Integer> supplier = new Supplier<Integer>() { @Override public Integer get() { return new Random().nextInt(100); } }; //lambda表达式 Supplier<Integer> supplier1 = ()-> { return new Random().nextInt(1000); }; int[] nums = getNums(supplier, 5); System.out.println(Arrays.toString(nums)); int[] nums1 = getNums(supplier1, 5); System.out.println(Arrays.toString(nums1)); int[] nums2 = getNums(()->new Random().nextInt(10), 5); System.out.println(Arrays.toString(nums2)); } //Consumer<T>消费型接口 public static void happy(Consumer<Double> consumer, Double money){ consumer.accept(money); } //Supplier<T>供给型接口 public static int[] getNums(Supplier<Integer> supplier,int count){ int[] arr = new int[count]; for (int i = 0; i < count; i++) { arr[i] = supplier.get(); } return arr; }}/* 执行结果:consumer唱歌消费了:1000.0consumer1唱歌消费了:1000.1consumer3吃饭消费了:2000.0=====================================================================[45, 71, 69, 5, 54][604, 149, 414, 618, 943][6, 1, 8, 3, 4]*/
代码2:
package com.wlw.chapter13_java8.demo01;import java.util.ArrayList;import java.util.List;import java.util.function.Function;import java.util.function.Predicate;public class Demo02 { public static void main(String[] args) { //匿名内部类 Function<String,String> function = new Function<String, String>() { @Override public String apply(String s) { return s.toUpperCase(); } }; //lambda表达式 Function<String,String> function1 = (s)-> { return s.trim(); }; String result = handlerString(function, “hello”); System.out.println(result); String result1 = handlerString(function1, ” hello zhangsan “); System.out.println(result1); String result2 = handlerString(s -> s.toLowerCase(),”HELLOWORLD”); System.out.println(result2); System.out.println(“===============================================================”); //匿名内部类 Predicate<String> predicate = new Predicate<String>() { @Override public boolean test(String s) { return s.startsWith(“zhang”); } }; List<String> list = new ArrayList<>(); list.add(“zhangwuji”); list.add(“zhangsan”); list.add(“zhangxiaofan”); list.add(“wangwu”); list.add(“lisi”); //lambda表达式 Predicate<String> predicate1 = (s)->{ return s.startsWith(“zhang”); }; List<String> resultlist = filterNames(predicate, list); System.out.println(resultlist); List<String> resultlist1 = filterNames(predicate1, list); System.out.println(resultlist1); List<String> resultlist2 = filterNames(s -> s.length()>7, list); System.out.println(resultlist2); } //Function<T,R>函数型接口 R apply(T t); public static String handlerString(Function<String,String> function,String str){ return function.apply(str); } //Predicate<T>断言型接口 public static List<String> filterNames(Predicate<String> predicate,List<String> list){ List<String> list1 = new ArrayList<>(); for (String result : list){ if(predicate.test(result)){ list1.add(result); } } return list1; }}/*执行结果:HELLOhello zhangsanhelloworld===============================================================[zhangwuji, zhangsan, zhangxiaofan][zhangwuji, zhangsan, zhangxiaofan][zhangwuji, zhangsan, zhangxiaofan]*/
失败是成功之母
