10.30作业.

static属性和方法如何调用:

public class p {
    private String name;
    private int age;
    static String city ="A城";
    public p(String name,int age) {
        this.name=name;
        this.age=age;
    }
    public String getInfo() {
        return "姓名:"+this.name+",年龄:"+this.age+",城市:"+city;
    }
}

public class qq {
    public static void main(String args[]) {
        p p1=new p("小明",30);
        p p2=new p("小白",21);
        p p3=new p("小红",34);
        System.out.println("===分界线===");
        System.out.println(p1.getInfo());
        System.out.println(p2.getInfo());
        System.out.println(p3.getInfo());
        System.out.println("===分界线===");    
        p.city="B城";
        System.out.println(p1.getInfo());
        System.out.println(p2.getInfo());
        System.out.println(p3.getInfo());
    }

}

构造方法私有化（饿汉式）

public class ww {
    private static ww instance=new ww();
    private ww() {
        
    }
    public static ww getInstance() {
        return instance;
    }
    public void print() {
        System.out.println("君不见");
        System.out.println("黄河之水天上来");
        System.out.println("奔流到海不复回");
        System.out.println("诗仙李白");
    }
}

public class ee {
    public static void main(String args[]) {
        ww s=null;
        s=ww.getInstance();
        s.print();
    }

}

空参构造自动命名（有参构造）

 

public class aa {
    private String name;
    private static int count;
    public aa() {
        count++;
        this.name="NONAME - "+count;
        
    }
    public aa(String name) {
        this.name=name;
    }
    public String getInfo() {
        return "姓名:" +this.name;
    }

}

public class zz {
    public static void main(String args[]) {
        System.out.println(new aa().getInfo());
        System.out.println(new aa("A").getInfo());
        System.out.println(new aa("B").getInfo());
        System.out.println(new aa().getInfo());
        
    }

}

空参构造输出个数---static关键字

public class ss {
    private String name;
    private static int count;
    public ss() {
        count++;
        System.out.println("地上有"+count+"朵花");
    }
    public String getInfo() {
        return "姓名:" +this.name;
    }

}

public class xx {
    public static void main(String args[]) {
        new ss();
        new ss();
        new ss();
        new ss();
    }

}

子父类

abstract class TT {
    public TT() {
        this.print();
        }
    public abstract void print();
    }
class B extends TT {
    private int x=100;
    public B(int x) {
        this.x=x;
        }
    public void print() {
        System.out.println("x - "+x);
        }

    }

public class UU {
        public static void main(String args[]) {
            TT a=new B(10);
        }

}