java之静态代码块、构造块、构造方法的简单例子

啥也不说直接贴代码！

public class Person {

private String name;

private int age;

public Person() {
System.out.println("this is a person");
}

{
System.out.println("this is a constructor block");
}

static {
System.out.println("this is a staitc block");
}

public Person(String name, int age) {
this();
this.name = name;
this.age = age;
System.out.println("his name is " + this.name + "his age is"
+ this.age);
}

public static void main(String args[]) {
Person a = new Person();
Person b = new Person("haha", 18);
}

}

运行结果如下：

this is a staitc block
this is a constructor block
this is a person
this is a constructor block
this is a person
his name is haha  his age is 18

可以发现静态代码块是最先执行的，而且仅仅执行一次，在伪编译生成.class文件的时间就运行。

接下来是构造块的执行，最然后是构造方法的执行，随着生成新的实例，构造块每次都会执行一次。

public class Test {
static {
System.out.println("hello world");
System.exit(1);
}
}

类似于这段代码，但是在java8中已经不能运行了。