初学者有关问题！请高手解决_J2SE

菜鸟问题！！请高手解决！
class SuperClass
{
public SuperClass()
{
}
public SuperClass(String s)
{
s=" ";
}
public void doSomething()
{
System.out.println("这是SuperClass输出的!");
}
}
class SubClass1 extends SuperClass
{
public void doSomething()
{
System.out.println("这是SubClass1输出的！");
}
public void doSth1()
{
System.out.println("这是doSth1输出的！");
}
}
class SubClass2 extends SuperClass
{
public void doSomething()
{
System.out.println("这是SubClass2输出的！");
}
public void doSth1()
{
System.out.println("这是doSth2输出的！");
}
}
public class testLayer
{
public static void main(String arge[])
{
SuperClass x = new SuperClass();
SuperClass y = new SubClass1();
SuperClass z = new SubClass2();
x.doSomething();
y.doSth1();
z.doSth2();
}
}
请高手改正！！谢谢！

------解决方案--------------------

Java code

class SuperClass {    public SuperClass() {    }    public SuperClass(String s) {        s = "   ";    }    public void doSomething() {        System.out.println("这是SuperClass输出的!");    }    public void doSth1() {        // TODO Auto-generated method stub    }}class SubClass1 extends SuperClass {    public void doSomething() {        System.out.println("这是SubClass1输出的！");    }    public void doSth1() {        System.out.println("这是doSth1输出的！");    }}class SubClass2 extends SuperClass {    public void doSomething() {        System.out.println("这是SubClass2输出的！");    }    public void doSth1() {        System.out.println("这是doSth2输出的！");    }}public class testLayer {    public static void main(String arge[]) {        SuperClass x = new SuperClass();        SuperClass y = new SubClass1();        SuperClass z = new SubClass2();        x.doSomething();        y.doSomething();        z.doSomething();        y.doSth1();        z.doSth1();    }}
------解决方案--------------------
Java code  public static void main(String arge[]) {    SuperClass x = new SuperClass();    SuperClass y = new SubClass1()f");try{fff b=new fff();b.method();}catch(NoSuchMethodException e){e.printStackTrace();}}}class fff{}
------解决方案--------------------
Java codeSuperClass z = new SubClass2();
------解决方案--------------------
你重写父类的方法，用父类的引用是可以调用的．而且调用的是子类里的方法，父类的方法被屏蔽了．但是父类看不到子类里的方法，所以父类的引用指向子类的对象，也调用不到子类里的方法的．只能子类自己的对象调用自己的方法．

Java codeclass SuperClass {    public SuperClass() {    }    public SuperClass(String s) {        s = "   ";    }    public void doSomething() {        System.out.println("这是SuperClass输出的!");    }}class SubClass1 extends SuperClass {    public void doSomething() {        System.out.println("这是SubClass1输出的！");    }    public void doSth1() {        System.out.println("这是doSth1输出的！");    }}class SubClass2 extends SuperClass {    public void doSomething() {        System.out.println("这是SubClass2输出的！");    }    public void doSth2() {        System.out.println("这是doSth2输出的！");    }}public class testLayer {    public static void main(String arge[]) {        SuperClass x = new SuperClass();        SuperClass y = new SubClass1();        SuperClass z = new SubClass2();        SubClass1 a = new SubClass1();        SubClass2 b = new SubClass2();        x.doSomething();        y.doSomething();//父类的方法被屏蔽了，调用的是子类里的方法        z.doSomething();//父类的方法被屏蔽了，调用的是子类里的方法        //y.doSth1();这里是不可见的，所以不能调用        //z.doSth2();这里是不可见的，所以不能调用        a.doSth1();        b.doSth2();    }}