java 接口访问

interface 接口访问 Dream.HOBBY.toString

package zh.codegym.task.task13.task1305;

/* 
四个错误
*/

public class Solution {

    public static void main(String[] args) {

        System.out.println(Dream.HOBBY.toString());
        System.out.println(new Hobby().toString());

    }

    interface Desire {
    }

    interface Dream {
        public static Hobby HOBBY = new Hobby();
    }

    static class Hobby implements Desire,Dream {
        static int INDEX = 1;

        @Override
        public String toString() {
            INDEX++;
            return "" + INDEX;
        }
    }

}
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类名和方法名一致this指向类。

package zh.codegym.task.task13.task1306;

/* 
有问题的 initializeIdAndName
*/

public class Solution {
    public static void main(String[] args) throws Exception {
        System.out.println(Matrix.NEO);
        System.out.println(Matrix.TRINITY);
    }

    static class Matrix {
        public static DBObject NEO = new User().initializeIdAndName(1, "Neo");
        public static DBObject TRINITY = new User().initializeIdAndName(2, "Trinity");
    }

    interface DBObject {
        DBObject initializeIdAndName(long id, String name);
    }

    static class User implements DBObject {
        long id;
        String name;

        public User initializeIdAndName(long id, String name) {
            this.id = id;
            this.name = name;
            return this;
        }

        @Override
        public String toString() {
            return String.format("用户名为 %s, id = %d", name, id);
        }
    }
}

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boolean 可以返回两个值true、false

package zh.codegym.task.task13.task1308;

/* 
嘿，你还活着吗？
*/

public class Solution {
    public static void main(String[] args) throws Exception {
    }

    public interface Person {
        boolean isAlive();
    }

    public interface Presentable extends Person {
    }
}

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