Java程序员的日常 —— static的用法讲解实践

package xing.test.thinking.chap5;
class A{
    public A() {
        System.out.println("A constructor");
    }
}

class VarTest{
    static A a = new A();
    public static int b = 0;
    public int c = 0;
    static{
        System.out.println("VarTest static");
    }
    public VarTest() {
        System.out.println("VarTest constructor");
    }
    public static void test(){
        System.out.println("in static test func");
    }
}
public class StaticTest {
    public static void main(String[] args) {
        System.out.println("start testing!");
        System.out.println("如果不new VarTest或者使用VarTest的静态内容，就不会触发VarTest静态块的执行");
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        VarTest.test();//也会触发静态块的执行
        
        VarTest testa = new VarTest();
        VarTest testb = new VarTest();
        System.out.println("testa.b: "+testa.b);
        System.out.println("testb.b: "+testb.b);
        System.out.println("testa.c: "+testa.c);
        System.out.println("testb.c: "+testb.c);
        //如果修改b属性的值，所有对象的内容都会改变
        testa.b = 3;
        System.out.println("testa.b: "+testa.b);
        System.out.println("testb.b: "+testb.b);
    }
}

start testing!
如果不new VarTest或者使用VarTest的静态内容，就不会触发VarTest静态块的执行
A constructor
VarTest static
in static test func
VarTest constructor
VarTest constructor
testa.b: 0
testb.b: 0
testa.c: 0
testb.c: 0
testa.b: 3
testb.b: 3