目录

Annotation

AnnotationDemo

FunctionInterfaceDemo

MetaAnnotation

Test

Lambda

Demo1

Demo2

Demo3

Stream

StreamDemo

Student

Annotation

AnnotationDemo

  @Auther:kongshan
    @Date:2022/5/15-05-15-17:00
    @Description:IntelliJ IDEA
    @version:


*/

import java.util.Date;

public class AnnotationDemo {
    private int num;

    @Override
    public String toString() {
        return "AnnotationDemo{" +
                "num=" + num +
                '}';
    }

public int add(int num,int num2){
    return num+num2;
}
@Deprecated
    public void test(){
    System.out.println("test");
}

    public static void main(String[] args) {
        AnnotationDemo ad=new AnnotationDemo();
//        ad.test();
        //使用反射技术创建对象
        try {
            AnnotationDemo ad2=(AnnotationDemo)Class.forName("class4.class_StreamAPI").newInstance();
        ad2.test();
        } catch (Exception e) {
            e.printStackTrace();
         }
        Date date=new Date();
        System.out.println(date.getYear());
    }
}

FunctionInterfaceDemo

   @Auther:kongshan
    @Date:2022/5/15-05-15-17:13
    @Description:IntelliJ IDEA
    @version:


*/
@FunctionalInterface
public interface FunctionInterfaceDemo {
    void suv(int a,int b);
}

MetaAnnotation

  @Auther:kongshan
    @Date:2022/5/15-05-15-17:14
    @Description:IntelliJ IDEA
    @version:


*/

import java.lang.annotation.*;

@MyAnnotation(age=20,joys = {"a","b","c"})
public class MetaAnnotation {
    public void print(){
        System.out.println("print.......");
    }
}
//自定义注解
//target是说明自定义注解在什么位置可以使用，包、类、方法、属性等等
@Target({ElementType.METHOD,ElementType.TYPE})
//retention说明当前注解可以使用的环境，或者说什么级别保存注释信息，有三个级别，源码级别SOURCE,类级别CLASS，运行时环境RUNTIME,默认一般是RUNTIME级别
@Retention(RetentionPolicy.RUNTIME)
//说明注解是否可以像是在javadoc中
@Documented
//说明当前注释是否能被继承
@Inherited
@interface MyAnnotation{
    //定义的方式看起来像是方法，但是实际上在使用注解的时候需要配置的一些参数名称和类型，默认的是value；
    //自定义注解的中填写的参数名称对应方法名，参数的类型对应方法的返回类型需要一个一个的添加，写起来很麻烦，因此一般给它一些默认值
    int id()default 1;
    String name()default "";
    int age()default 18;
    String []joys() default "";
}

Test

 @Auther:kongshan
    @Date:2022/5/15-05-15-17:26
    @Description:IntelliJ IDEA
    @version:


*/

public class Test {
    public void test(){
        System.out.println("test");
        }
  }

Lambda

Demo1

 @Auther:kongshan
    @Date:2022/5/15-05-15-19:21
    @Description:IntelliJ IDEA
    @version:


*/

import java.util.function.*;

;

public class Demo1 {
    public void getNum(Object num){
        System.out.println("getNum"+num);
    }
    public String toUpperCase(String str){
        return str.toUpperCase();
    }
    public Integer getLength(String str1,String str2){
        return str1.length()+str2.length();
    }
    public int get(){
        return 1;
    }

    public static void main(String[] args) {
//        new Demo1().getNum(100);
        //使用new关键字示例（instance）化一个对象
//        Demo1 d=new Demo1();

        Consumer c1=(num)->new Demo1().getNum(num);
        Consumer c2=new Demo1()::getNum;
        c1.accept(200);
        c2.accept(300);
        Function f1 = (str)->str.toUpperCase();
        Functionf2=(str)->new Demo1().toUpperCase(str);
        Function f3 =new Demo1()::toUpperCase;
        System.out.println(f1.apply("abcdefg"));
        System.out.println(f2.apply("abc"));
        System.out.println(f3.apply("abc"));

        UnaryOperatoruo=(str)->new Demo1().toUpperCase(str);
        UnaryOperatoruo2=new Demo1()::toUpperCase;
        System.out.println(uo.apply("abcdefghijk"));
        System.out.println(uo2.apply("abcd"));

        BiFunctionbf1=new BiFunction() {
            @Override
            public Integer apply(String s, String s2) {
                return new Demo1().getLength(s,s2);
            }
        };
        System.out.println(bf1.apply("空衫","加油"));
        BiFunctionbf2=(str1,str2)->new Demo1().getLength(str1,str2);
        BiFunctionbf3=new Demo1()::getLength;
        BiFunctionbf4=(str1,str2)->{
            return new Demo1().getLength(str1,str2);
        };
        System.out.println(bf2.apply("abc","bcd"));
        System.out.println(bf3.apply("空衫","加油"));
        System.out.println(bf4.apply("空衫","666"));
        Suppliers1=new Demo1()::get;
        System.out.println(s1.get());

    }
}

Demo2

  @Auther:kongshan
    @Date:2022/5/15-05-15-19:49
    @Description:IntelliJ IDEA
    @version:


*/
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;

public class Demo2 {
    public static void main(String[] args) {
    Consumer c1=new Consumer(){

        @Override
        public void accept(Foo foo) {
//            new Foo().get();
//            new Foo().get();
            foo.get();
        }
    };
    c1.accept(new Foo());
    Consumerc2=(foo)->new Foo().get();
    Consumerc3=(foo)->new Foo().get();
    Consumerc4=(foo)->new Foo().get();
    Consumerc5=(foo)->new Foo().get();
    c2.accept(new Foo());
    c3.accept(new Foo());
    c4.accept(new Foo());
    c5.accept(new Foo());
        Functionf1=(foo)->new Foo().print();
        Functionf2=Foo::print;
        f1.apply(new Foo());
        f2.apply(new Foo());
        BiConsumer bc1=(foo, name)->new Foo2().show(name);
        BiConsumerbc2=Foo2::show;
//        BiConsumerbc3=Foo2::show;错误
        bc1.accept(new Foo2(),"zhaoyun");
        bc2.accept(new Foo2(),"guanyu");
    }
static class Foo{
        public void get(){
            System.out.println("foo--get");
        }
        public int print(){
            System.out.println("foo---print");
            return 1;
        }
}
 static class Foo2{
    public void get(){
        System.out.println("foo2---get");
    }
    public int print(){
        System.out.println("foo2---print");
        return 2;
    }
    public void show(String name){
        System.out.println("foo2---show---"+name);
    }

    }
}

Demo3

   @Auther:kongshan
    @Date:2022/5/15-05-15-22:54
    @Description:IntelliJ IDEA
    @version:


*/


import java.util.Arrays;
import java.util.List;
import java.util.function.Function;
import java.util.function.Supplier;

public class Demo3 {
    public static void main(String[] args) {
        Suppliers1=new Supplier() {
            @Override
            public Person get() {
                return new Person();
            }
        };
        s1.get();
        Supplier s2 = ()->new Person();
        Supplier s3 = ()->{return new Person();};
        Supplier s4 = Person::new;
        s2.get();
        s3.get();
        s4.get();


        Functionf=new Function() {
            @Override
            public User apply(String s) {
                return new User(s);
            }
        };
        Functionf1=(name)->new User(name);
        Functionf2=User::new;
        f1.apply("zhangsan");
        f2.apply("guanyu");
        Functionf3=(age)->new User(age);
        Functionf4=User::new;
        f3.apply(25);
        f4.apply(30);
        Listlist= Arrays.asList("a","b","c","d","e");
        list.forEach(System.out::println);


    }

}
class User{
    public User(){
        System.out.println("User的空构造方法被调用了.....");
    }
    public User(String naem){
        System.out.println("User含有name的构造方法被调用了....");
    }
    public User(int age){
        System.out.println("User含有age的构造方法被调用了.....");
    }
}
class Person{
    public Person(){
        System.out.println("Person的空构造方法被调用了");
    }

}

Stream

StreamDemo

 @Auther:kongshan
    @Date:2022/5/16-05-16-10:01
    @Description:IntelliJ IDEA
    @version:


*/

import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class StreamDemo {
    //通过数组生成
    public static void generate1(){
        String []str={"a","b","c","d","e" };
        StreamstringStream=Stream.of(str);
        stringStream.forEach(System.out::println);
    }
    //通过集合生成
    public static void generate2(){
        Listlist= Arrays.asList(1,2,3,4,5);
        Streamstream=list.stream();
        stream.forEach(System.out::println);
    }
    //通过generate生成
    public static void generate3(){
//        生成10个1
        Streamstream=Stream.generate(()->1);
        stream.limit(10).forEach(System.out::println);
    }
    public static void generate4(){
//        生成1-10的整数
        Streamstream=Stream.generate(()->{
            int i=1;
            for (int j = 0; j <100 ; j++) {
                System.out.println(j);
            }
            return i;
        });

        Streamstream1=Stream.iterate(1,(x)->x+1);
        stream1.limit(10).forEach(System.out::println);
    }
//    通过其他API创建
    public static void generate5(){
        String str="abcdefg";
        IntStream intStream=str.chars();
        intStream.forEach(System.out::println);
    }

    public static void main(String[] args) {
        Listlist =Arrays.asList("go","java","python","scala","javascript");
        list.forEach(System.out::println);
        generate1();
        generate2();
        generate3();
        System.out.println("********************");
        generate4();
        generate5();
//        中间操作：如果调用方法之后返回的结果是Stream对象就意味着是一个中间操作
        Arrays.asList(1,2,3,4,5,6).stream().filter(x->x%2==0).forEach(System.out::println);
        System.out.println("********************");
//        原来的写法
        Listlist2=Arrays.asList(1,2,3,4,5,6);
//        1.for循环遍历
        for (int i=0;iiteratorIterator=list2.iterator();
        while (iteratorIterator.hasNext()){
            Integer next=iteratorIterator.next();
            if (next%2==0){
                System.out.println(next);
            }
        }
//        3.增强for循环
        for (Integer integer:list2){
            if (integer%2==0){
                System.out.println(integer);
            }
        }
        Listlist1=Arrays.asList(1,2,3,4,5,6);
//        求出结果集中所有偶数的和
        int sum=list1.stream().filter(x->x%2==0).mapToInt(x->x).sum();
        System.out.println(sum);
//求集合中的最大值
        Optionalmax=list1.stream().max((a,b)->a-b);
        System.out.println(max.get());
//        求集合的最小值
        Optionalmin=list1.stream().min((a,b)->a-b);
        System.out.println(min.get());

        //        原来的写法？
        Optionalany=list1.stream().filter(x->x%2==0).findAny();
        System.out.println(any.get());
        Optionalfirst=list1.stream().filter(x->x%10==6).findFirst();
        System.out.println(first.get());
        StreamintegerStream=list1.stream().filter(i->{
            System.out.println("代码运行！");
            return i%2==0;
        });
        integerStream.findFirst();
        System.out.println(integerStream.findFirst().get());
        System.out.println(integerStream.findAny().get());
        //获取最大值和最小值但是不适用min和max方法
        Optionalmin2=list1.stream().sorted().findFirst();
        System.out.println(min2.get());
        Optionalmax2=list1.stream().sorted((a,b)->b-a).findFirst();
        System.out.println(max2.get());
        Arrays.asList("go","python","scala","java","javascript").stream().sorted().forEach(System.out::println);
        Arrays.asList("go","python","scala","java","javascript").stream().sorted((a,b)->a.length()-b.length()).forEach(System.out::println);


//        原来的写法？如果不适用比较器如何写代码
//        想将集合中的元素进行过滤的同时返回一个集合对象
        Listlist3=list1.stream().filter(x->x%2==0).collect(Collectors.toList());
        list3.forEach(System.out::println);
//        去重操作
        StreamintegerStream1=Arrays.asList(1,2,3,4,5,6,7,8,9).stream().distinct();
        integerStream1.forEach(System.out::println);
        //打印20-30这样的集合数据
        Stream.iterate(1,x->x+1).limit(30).skip(20).limit(10).forEach(System.out::println);
        String str="10,20,30,40,50,60";
        //原来的写法？
        String[]strs=str.split(",");
        int sum1=0;
        for (String s:strs){
            sum1+=Integer.valueOf(s);
    }
        System.out.println(sum1);
        System.out.println(Stream.of(str.split(",")).mapToInt(x->Integer.valueOf(x)).sum());
        System.out.println(Stream.of(str.split(",")).mapToInt(Integer::valueOf).sum());
        System.out.println(Stream.of(str.split(",")).map(x->Integer.valueOf(x)).mapToInt(x->x).sum());
        System.out.println(Stream.of(str.split(",")).map(Integer::valueOf).mapToInt(x->x).sum());

//        创建一组自定义对象
        String names="张三,李四,王二,麻子,空衫";
        //原来的写法
        String []nameArray=names.split(",");
        Student student=new Student();
        for (String s:nameArray){
            student.setName(s);
            System.out.println(student);
        }
        Stream.of(names.split(",")).map(name->new Student(name)).forEach(System.out::println);
        Stream.of(names.split(",")).map(Student::new).forEach(System.out::println);
        System.out.println("*************************");
        Stream.of(names.split(",")).map(name->Student.getStudent(name)).forEach(System.out::println);
        Stream.of(names.split(",")).map(Student::getStudent).forEach(System.out::println);
//        将str中的每一个数值都打印出来，同时算出最终的求和结果
        String str2="1,2,3,4,5,6,7,8,9";
        System.out.println(Stream.of(str2.split(",")).peek(System.out::println).mapToInt(Integer::valueOf).sum());
        System.out.println(list1.stream().allMatch(x->x>2));
        System.out.println(list1.stream().anyMatch(x->x>2));
        System.out.println(list1.stream().count());
    }

}

Student

 @Auther:kongshan
    @Date:2022/5/16-05-16-10:34
    @Description:IntelliJ IDEA
    @version:


*/

public class Student {
    private String name;

    public Student() {
    }

    public Student(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    public static Student getStudent(String name){
        Student student=new Student();
        student.setName(name);
        return student;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + ''' +
                '}';
    }
}