[java]代码块

0,局部代码库--限制变量生命周期

1.构造代码块--抽取构造方法相同部分

2,全局代码块

3,静态代码块--只执行1次,随着class文件加载而加载.

加载顺序:
静态代码块-->构造代码块-->构造方法

package com.ma.demo4;public class Demo {static {System.out.println("demo全局静态代码块");}{System.out.println("demo全局代码块");}public Demo() {System.out.println("demo无参数构造");}public Demo(int a) {System.out.println("demo int i数构造");}void show() {{System.out.println("demo局部代码块");}System.out.println("demo show");}}---

package com.ma.demo4;public class Test {public static void main(String[] args) {Demo dd = new Demo(100);dd.show();System.out.println("++++++++++++++++++++++++++++++++++++++++");Demo dd2 = new Demo(100);dd.show();{System.out.println("main局部代码块(非静态)");}}static {System.out.println("main全局静态代码块");}}

执行结果:

main全局静态代码块demo全局静态代码块demo全局代码块demo int i数构造demo局部代码块demo show++++++++++++++++++++++++++++++++++++++++demo全局代码块demo int i数构造demo局部代码块demo showmain局部代码块(非静态)