函数式接口：只有一个抽象方法的接口

 

一、lambda表达式（方法参数为函数式接口）

1.无参

public interface MyFunctionalInterface {    void method();}

public class TestJdk8 {    public static void show(MyFunctionalInterface myInter) {        myInter.method();    }    public static void main(String[] args) {        show(() -> System.out.println("使用无参lambda表达式"));    }}

2.创建线程

public class TestJdk8 {    public static void startThread(Runnable runnable) {        new Thread(runnable).start();    }    public static void main(String[] args) {        startThread(() -> System.out.println(Thread.currentThread().getName() + " --> 线程启动了"));    }}

3.Supplier接口

public class TestJdk8 {    public static String getStr(Supplier
     
       sup) {        return sup.get();    }    public static void main(String[] args) {        String str = getStr(() -> "头条");        System.out.println(str);    }}
     

 4.Consumer接口

public class TestJdk8 {    public static void method(String name, Consumer
     
       con) {        con.accept(name);    }    public static void main(String[] args) {        method("百度", name -> System.out.println(name));    }}
     

5.Predicate接口

public class TestJdk8 {    public static boolean checkStr(String str, Predicate
     
       pre) {        return pre.test(str);    }    public static void main(String[] args) {        boolean b = checkStr("abcde", str -> str.length() > 5);        System.out.println(b);    }}
     

6.Function接口（类型转换）

public class TestJdk8 {    public static void change(String str, Function
     
       fun) {        Integer i = fun.apply(str);        System.out.println(i + 1);    }    public static void main(String[] args) {        change("1234", s -> Integer.parseInt(s));    }}
     

 

二、stream流

1.foreach

public class TestJdk8 {    public static void main(String[] args) {        Stream
     
       stream = Stream.of("张三", "李四", "王五", "赵六", "田七");        stream.forEach(name -> System.out.println(name));    }}
     

2.filter（底层是Predicate接口）

public class TestJdk8 {    public static void main(String[] args) {        Stream
     
       stream = Stream.of("张三丰", "张无忌", "赵敏", "周芷若", "张翠山", "张三");        stream.filter(name -> name.startsWith("张"))                .filter(name -> name.length() > 2)                .forEach(name -> System.out.println(name));    }}
     

3.map(底层是Function接口)

public class TestJdk8 {    public static void main(String[] args) {        Stream
     
       stream = Stream.of("1", "2", "3", "4");        stream.map(s -> Integer.parseInt(s) + 2)                .forEach(i -> System.out.println(i));    }}
     

4.count

public class TestJdk8 {    public static void main(String[] args) {        Stream
     
       stream = Stream.of("张三丰", "张无忌", "赵敏", "周芷若", "张翠山", "张三");        System.out.println(stream.count());    }}
     

5.limit(skip方法与之相反，不再赘述)

public class TestJdk8 {    public static void main(String[] args) {        ArrayList
     
       list = new ArrayList<>();        list.add("美羊羊");        list.add("喜羊羊");        list.add("懒羊羊");        list.add("沸羊羊");        list.add("灰太狼");        list.add("红太狼");        list.stream().limit(5).forEach(s -> System.out.println(s));    }}
     

6.collect（转换为集合）

List
     
       platformChannelInfos = platformChannelPOs.stream()                .map(platformChannelPO -> PlatformChannelPoConverter.po2Bo(platformChannelPO))                .collect(Collectors.toList());
     

 

三、方法引用

 1.sout

public class TestJdk8 {    public static void main(String[] args) {        ArrayList
     
       list = new ArrayList<>();        list.add("美羊羊");        list.add("喜羊羊");        list.add("懒羊羊");        list.stream().forEach(System.out::println);    }}
     

2.静态方法

public interface Calculate {    int calAbs(int num);}

public class TestJdk8 {    public static int method(int num, Calculate c) {        return c.calAbs(num);    }    public static void main(String[] args) {        System.out.println(method(-8, Math::abs));    }}

3.构造方法

public class Person {    private String name;    public Person() {    }    public Person(String name) {        this.name = name;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

public interface PersonBuilder {    Person buildPerson(String name);}

public class TestJdk8 {    public static void buildPerson(String name, PersonBuilder pb) {        Person person = pb.buildPerson(name);        System.out.println(person + person.getName());    }    public static void main(String[] args) {        buildPerson("张学友", Person::new);    }}

4.构造数组

public interface ArrayBuilder {    int[] buildArray(int length);}

public class TestJdk8 {    public static int[] creatArray(int length, ArrayBuilder ab) {        return ab.buildArray(length);    }    public static void main(String[] args) {        int[] array = creatArray(12, int[]::new);        System.out.println(array.length);    }}