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); } }