Java8-functionInterface Lambda表达式用法用户范例package com.example.study.java8.InterfaceFunction; /** * lambda表达式用法 */ public class LambdaUsage { public static void main(String[] args) { Runnable runnable1 = ()-> System.out.println("hello"); Runnable runnable2 = new Runnable() { @Override public void run() { System.out.println("hello"); } }; process(runnable1); process(runnable2); process(()-> System.out.println("hello")); } public static void process(Runnable runnable){ runnable.run(); } } 学习目标一、Predicate：诊断，返回boolean类型@FunctionalInterface public interface Predicate {/** * Evaluates this predicate on the given argument. * * @param t the input argument * @return {@code true} if the input argument matches the predicate, * otherwise {@code false} */ boolean test(T t);二、Consumer：消费者，没有返回类型@FunctionalInterface public interface Consumer {/** * Performs this operation on the given argument. * * @param t the input argument */ void accept(T t);三、Function：函数有返回值@FunctionalInterface public interface Function<T, R> {/** * Applies this function to the given argument. * * @param t the function argument * @return the function result */ R apply(T t);四、Supplier：生成者：返回一个对象@FunctionalInterface public interface Supplier {/** * Gets a result. * * @return a result */ T get();详细说明1、Predicate详细用法范例： package com.example.study.java8.InterfaceFunction; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.function.BiPredicate; import java.util.function.IntPredicate; import java.util.function.Predicate; /** * Lambda表达式的使用:Prodicate用法 */ public class LambdaUsagePredicate { public static void main(String[] args) { List<Apple> list = Arrays.asList(new Apple("red", 10) , new Apple("red", 60) , new Apple("blue", 40) , new Apple("black", 30) , new Apple("green", 80) , new Apple("blue", 90) , new Apple("green", 60) , new Apple("green", 50) , new Apple("red", 20)); //Predicate用法 List<Apple> filterList = filter(list, apple -> apple.getColor().equals("green")); for (Apple apple : filterList) { System.out.println(apple.toString()); } System.out.println("============================"); //其它类似Predicate用法 //IntegerPredicate用法 List<Apple> filterByWeight = predicateByWeight(list, weight -> weight == 60); for (Apple apple : filterByWeight) { System.out.println(apple.toString()); } System.out.println("============================"); //BiPredicate用法 List<Apple> biPredicateResult = biPredicateByColorAndWeight(list, (color, weight) -> { return color.equals("green") && weight == 60; }); for (Apple apple : biPredicateResult) { System.out.println(apple.toString()); } } //1、Predicate：诊断的用法 public static List<Apple> filter(List<Apple> sources, Predicate<Apple> predicate) { List<Apple> result = new ArrayList<>(); for (Apple apple : sources) { if (predicate.test(apple)) { result.add(apple); } } return result; } //2、其它类似Predicate用法 //IntegerPredicate用法 public static List<Apple> predicateByWeight(List<Apple> source, IntPredicate intPredicate) { List<Apple> result = new ArrayList<>(); for (Apple apple : source) { if (intPredicate.test(apple.getWeight())) { result.add(apple); } } return result; } //3、带2个参数的BiPredicate用法 public static List<Apple> biPredicateByColorAndWeight(List<Apple> source, BiPredicate<String, Integer> biPredicate) { List<Apple> result = new ArrayList<Apple>(); for (Apple apple : source) { if (biPredicate.test(apple.getColor(), apple.getWeight())) { result.add(apple); } } return result; } } 2、Consumer详细用法范例： package com.example.study.java8.InterfaceFunction; import java.util.Arrays; import java.util.List; import java.util.function.BiConsumer; import java.util.function.Consumer; /** * Lambda表达式：Consumer用法 */ public class LambdaUasgeConsumer { public static void main(String[] args) { List<Apple> list = Arrays.asList(new Apple("red", 10) , new Apple("red", 60) , new Apple("blue", 40) , new Apple("black", 30) , new Apple("green", 80) , new Apple("blue", 90) , new Apple("green", 60) , new Apple("green", 50) , new Apple("red", 20)); //1个参数调用 simpleUsageConsumer(list, apple -> System.out.println(apple.toString())); System.out.println("========================"); twoArgsUsageConsumer("我买了水果",list, (apple, name)->{ System.out.println(name+",颜色:"+apple.getColor()+"\t 重量:"+apple.getWeight()); }); } //1、一个参数用法 public static void simpleUsageConsumer(List<Apple> source, Consumer<Apple> consumer) { for (Apple apple : source) { consumer.accept(apple); } } //2、两个参数用法 public static void twoArgsUsageConsumer(String name, List<Apple> source, BiConsumer<Apple, String> consumer) { for (Apple apple : source) { consumer.accept(apple, name); } } } 3、Funcation详细用法范例：package com.example.study.java8.InterfaceFunction; import java.util.ArrayList; import java.util.Arrays; import java.util.List; import java.util.function.BiFunction; import java.util.function.Function; import java.util.function.IntFunction; /** * Lambda表达式：Funcation用法 */ public class LambdaUsageFuncation { public static void main(String[] args) { List<Apple> list = Arrays.asList(new Apple("red", 10) , new Apple("red", 60) , new Apple("blue", 40) , new Apple("black", 30) , new Apple("green", 80) , new Apple("blue", 90) , new Apple("green", 60) , new Apple("green", 50) , new Apple("red", 20)); //1、2个参数调用 List<String> stringsUsageFuncation = simpleUsageFuncation(list, apple -> apple.getColor() + ":颜色"); for(String color: stringsUsageFuncation){ System.out.println(color); } System.out.println("============================"); //2、其它用法IntFuncation调用 List<Integer> integerList = intUsageFuncation(list, weight-> weight*20); for(Integer i : integerList){ System.out.println(i); } System.out.println("=============================="); //3、3个参数调用 Apple newApple = threeeUsageFuncation("彩色", 178, (newColor, newInteger) -> { return new Apple(newColor, newInteger); }); System.out.println(newApple.toString()); } //1、2个参数 简单用法 public static List<String> simpleUsageFuncation(List<Apple> source, Function<Apple, String> function){ List<String > result = new ArrayList<>(); for(Apple apple:source){ result.add(function.apply(apple)); } return result; } //2、其它用法IntFuncation public static List<Integer> intUsageFuncation(List<Apple> source, IntFunction<Integer> function){ List<Integer > result = new ArrayList<>(); for(Apple apple:source){ result.add(function.apply(apple.getWeight())); } return result; } //3、3个参数用法 public static Apple threeeUsageFuncation(String newColor, Integer newWeight, BiFunction<String, Integer, Apple> biFunction){ return biFunction.apply(newColor, newWeight); } } 4、Supplier详细用户范例：package com.example.study.java8.InterfaceFunction; import java.util.function.Supplier; /** * Lamdba表达式之Supplier用法 */ public class LambdaUsageSupplier { public static void main(String[] args) { //范例1 Supplier<String> stringSuppier = String::new; System.out.println(stringSuppier.get().getClass()); System.out.println("====================="); //范例2 Apple apple = createApple(() -> { return new Apple("五颜六色", 200); }); System.out.println(apple.toString()); } public static Apple createApple(Supplier<Apple> supplier){ return supplier.get(); } } 注意：参数类型package com.example.study.java8.InterfaceFunction; /** * 参数类型注意 */ public class ArgsCase { public static void main(String[] args) { int i =0; Runnable runnable = new Runnable() { @Override public void run() { //i会报错提示： //Variable 'i' is accessed from within inner class, needs to be final or effectively final // i++; } }; i++; //Lambda表达式 Runnable runnable1 = ()->{ //i同样报错提示： //Variable used in lambda expression should be final or effectively final // System.out.println(i); }; i++; } }