java注解

package com.atguigu.java;
//自定义的注解
public @interface MyAnnotation {
     String value() default "hello";
}

package com.atguigu.java;
import java.util.ArrayList;
import java.util.List;
/*
 * 注解
 * 1.JDK提供的常用的注解
 *   @Override:限定重写父类方法，该注释只能用于方法
 *   @Deprecated:用于表示某个程序元素（类，方法等）已过时
 *   @SupressWarnings:抑制编译器警告
 * 2.如何自定义一个注释
 * 3.元注解
 * */
public class TestAnnotation {
    public static void main(String[] args){
        Person person=new Student("tom",21);
        person.walk();
        person.eat();
        
        @SuppressWarnings({ "unused", "rawtypes" })
        List list=new ArrayList();
        
        @SuppressWarnings("unused")
        int i=10;
    }
}
@MyAnnotation(value="atguigu")
class Student extends Person{
    public Student(String name, int age) {
        super(name, age);
    }
    @Override
    public void walk(){
        System.out.println("学生走路");
    }
    @Override
    public void eat(){
        System.out.println("学生吃饭");
    }
}
@Deprecated
class Person{
    private String name;
    private int age;
    @MyAnnotation(value="atguigu")
    public Person(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }
    @MyAnnotation(value="atguigu")
    public void walk(){
        System.out.println("走路");
    }
    @Deprecated
    public void eat(){
        System.out.println("吃饭");
    }
    @Override
    public String toString(){
        return "Person [name="+name+",age="+age+"]";
    }
} 

package com.atguigu.java;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.CONSTRUCTOR;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.ElementType.LOCAL_VARIABLE;
//自定义的注解
@Target({TYPE,FIELD,METHOD,PARAMETER,CONSTRUCTOR,LOCAL_VARIABLE})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
     String value() default "hello";
}