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);        }}