![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
子类和父类的定义如下: class A { int v1=10; int v2=10; public A() {} public A(int v1) { super(); } public void m1() { System.out.println("A m1"); } public void m2() { System.out.println("A m2"); } } class B extends A { int v2=20; int v3=20; public B() { } public void m2() { System.out.println("B m2"); } public void m3() { System.out.println("B m3"); } } 测试代码为: A a = new A(); a.m1(); a.m2(); System.out.println(a.v1); System.out.println(a.v2); 系统输出为: