Java面向对象高级2

1.代码块

2.内部类

成员内部类

    public class Demo{
        public static void main(String[] args) {
            outer.inner in=new outer().new inner();
            in.run();
        }
    }
    class outer{
        private String str="outer";
        public class inner{
            public void run(){
                String s=str;
                System.out.println(s);
            }
        }
    }

静态内部类

    public class Demo{
        public static void main(String[] args) {
            outer.inner in=new outer.inner();
            in.run();
        }
    }
    class outer{
        private static String str="outer";
        private String str2="outer";
        public static class inner{
            public void run(){
                String s=str;
               // String ss=str2; 静态内部类属于外部类无法访问外部成员变量，外部的成员变量属于对象，而不是属于外部类，
                //所以可以访问外部类的str,但无法访问属于对象的str2
                System.out.println(s);
            }
        }
    }

局部内部类

3.匿名内部类

//普通写法
public class Demo{
    public static void main(String[] args) {
        Animal c=new cat();
        c.cry();
    }
}
abstract class Animal{
    public abstract void cry();
}
class cat extends Animal{
    public void cry(){
        System.out.println("猫叫");
    }
}
//匿名类写法
public class Demo{
    public static void main(String[] args) {
    //匿名内部类实际上是有名字的：外部类名$编号.class
    //匿名内部类本质是一个子类，同时会立即创建一个子类对象。
        Animal c=new Animal() {
            @Override
            public void cry() {
                System.out.println("猫叫");
            }
        };
        c.cry();
    }
}
abstract class Animal{
    public abstract void cry();
}

//匿名类的反编译文件，该文件的名字为Demo$1.class
class Demo$1 extends Animal {
    Demo$1() {
    }

    public void cry() {
        System.out.println("猫叫");
    }
}

匿名内部类的常见使用形式

//非匿名类写法
public class Demo{
    public static void main(String[] args) {
        swimming s=new Student();
        doswim(s);
        swimming t=new Teacher();
        doswim(t);
    }
    public static void doswim(swimming s){
        s.swim();
    }
}
class Student implements swimming{
    public void swim(){
        System.out.println("学生游泳");
    }
}
class Teacher implements swimming{
    public void swim(){
        System.out.println("老师游泳");
    }
}
interface swimming{
    void swim();
}

//匿名类写法
public class Demo{
    public static void main(String[] args) {
        swimming s=new swimming() {
            @Override
            public void swim() {
                System.out.println("学生游泳");
            }
        };
        doswim(s);
        doswim(new swimming() {
            @Override
            public void swim() {
                System.out.println("老师游泳");
            }
        });
    }

    public static void doswim(swimming s){
        s.swim();
    }
}

interface swimming{
    void swim();
}

感觉就是有时候简化代码用的？

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Comparator;

public class Demo {
    public static void main(String[] args) {
        student[] s=new student[3];
        s[0]=new student("li hua",18);
        s[1]=new student("jack",16);
        s[2]=new student("red",21);
        Arrays.sort(s, new Comparator<student>() {
            @Override
            public int compare(student o1, student o2) {
                return o1.getAge()- o2.getAge();
            }
        });
        for(int i=0;i<s.length;i++){
            System.out.println(s[i].getAge());
        }
    }
}
class student{
    private String name;
    private int age;
    public student(){}
    public student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

4.函数式编程-Lambda

public class Demo{
    public static void main(String[] args) {
        swim s=()->{
            System.out.println("学生游泳");
        };
        s.swimming();
    }
}
@FunctionalInterface
interface swim{
    void swimming();
}

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Comparator;

public class Demo {
    public static void main(String[] args) {
        student[] s=new student[3];
        s[0]=new student("li hua",18);
        s[1]=new student("jack",16);
        s[2]=new student("red",21);
//        Arrays.sort(s, new Comparator<student>() {
//            @Override
//            public int compare(student o1, student o2) {
//                return o1.getAge()- o2.getAge();
//            }
//        });
        Arrays.sort(s,(student o1, student o2)->{
            return o1.getAge()- o2.getAge();
        });
        for(int i=0;i<s.length;i++){
            System.out.println(s[i].getAge());
        }
    }
}
class student{
    private String name;
    private int age;
    public student(){}
    public student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Comparator;

public class Demo {
    public static void main(String[] args) {
        student[] s=new student[3];
        s[0]=new student("li hua",18);
        s[1]=new student("jack",16);
        s[2]=new student("red",21);
//        Arrays.sort(s, new Comparator<student>() {
//            @Override
//            public int compare(student o1, student o2) {
//                return o1.getAge()- o2.getAge();
//            }
//        });


/*        Arrays.sort(s,(student o1, student o2)->{
            return o1.getAge()- o2.getAge();
        });
        */
        
        Arrays.sort(s,(o1,o2)->o1.getAge()- o2.getAge());
        for(int i=0;i<s.length;i++){
            System.out.println(s[i].getAge());
        }
    }
}
class student{
    private String name;
    private int age;
    public student(){}
    public student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

5.函数式编程-方法引用

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Comparator;

public class Demo {
    public static void main(String[] args) {
        student[] s=new student[3];
        s[0]=new student("li hua",18);
        s[1]=new student("jack",16);
        s[2]=new student("red",21);
//        Arrays.sort(s, new Comparator<student>() {
//            @Override
//            public int compare(student o1, student o2) {
//                return o1.getAge()- o2.getAge();
//            }
//        });


/*        Arrays.sort(s,(student o1, student o2)->{
            return o1.getAge()- o2.getAge();
        });
        */

 //       Arrays.sort(s,(o1,o2)->o1.getAge()- o2.getAge());

     //   Arrays.sort(s,(o1,o2)->student.CompareByAge(o1,o2));
        Arrays.sort(s, student::CompareByAge);
        for(int i=0;i<s.length;i++){
            System.out.println(s[i].getAge());
        }
    }
}
class student{
    private String name;
    private int age;
    public student(){}
    public static int CompareByAge(student o1, student o2){
        return o1.getAge()- o2.getAge();
    }
    public student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Comparator;

public class Demo {
    public static void main(String[] args) {
        student[] s=new student[3];
        s[0]=new student("li hua",18);
        s[1]=new student("jack",16);
        s[2]=new student("red",21);
//        Arrays.sort(s, new Comparator<student>() {
//            @Override
//            public int compare(student o1, student o2) {
//                return o1.getAge()- o2.getAge();
//            }
//        });


/*        Arrays.sort(s,(student o1, student o2)->{
            return o1.getAge()- o2.getAge();
        });
        */

 //       Arrays.sort(s,(o1,o2)->o1.getAge()- o2.getAge());

     //   Arrays.sort(s,(o1,o2)->student.CompareByAge(o1,o2));
//        Arrays.sort(s, student::CompareByAge);
        student t=new student();
        Arrays.sort(s, t::Compare);
        for(int i=0;i<s.length;i++){
            System.out.println(s[i].getAge());
        }
    }
}
class student{
    private String name;
    private int age;
    public student(){}
    public int Compare(student o1,student o2){
        return o1.getAge()-o2.getAge();
    }
    public static int CompareByAge(student o1, student o2){
        return o1.getAge()- o2.getAge();
    }
    public student(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

原文地址：https://blog.csdn.net/m0_53203911/article/details/143765785

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