用Java语言编写下面要求的程序

第一个类：父类MathAdd.java
public class MathAdd {
int a;
int b;
double c;
double d;

public MathAdd() {
}

// 整数的加法
public int add(int a, int b) {

return a + b;
}

// 加法的重载，实现double类型的数加法
public double add(double c, double d) {
this.c = c;
this.d = d;

return c + d;
}

public String toString() {
return "这是父类MathAdd！";
}

}

第二个类：子类ExtendsMathAdd.java
public class ExtendsMathAdd extends MathAdd {

//子类构造方法
public ExtendsMathAdd(){

}

//重写覆盖父类MathAdd中的toString方法
public String toString() {
return "这里是覆盖父类的方法，我是子类ExtendsMathAdd";
}

}

第三个类：测试类Test.java
public class Test {

public static void main(String[] args) {
//实例化父类
MathAdd ma = new MathAdd();
//实例化子类
ExtendsMathAdd ema = new ExtendsMathAdd();

System.out.println("测试父类整数的加法：4 + 5 = " + ma.add(4, 5));
System.out.println("测试父类double类型的加法：4.0 + 5.0 = " + ma.add(4.0, 5.0));
System.out.println("测试父类的toString方法" + ma);

System.out.println("测试子类继承的整数的加法：3 + 5 = " + ema.add(3, 5));
System.out.println("测试子类继承的double类型的加法：3.0 + 5.0 = " + ema.add(3.0, 5.0));
System.out.println("测试子类覆盖父类的toString方法" + ema);

}

}

/**
* @author qingsongwang
*
*/
public class DEmoop
{
public static void main(String[] wqs)
{
student4 st=new student4();
student1 st1=new student1();
st.print();
st.print("tom");
st1.print();
}

}

class student4 extends student1
{
public void print()
{
System.out.println("这是我的同学");
}
public void print(String name)
{
System.out.println("这是小明的同学"+name);
}
}
///学生类1
class student1
{
public void print()
{
System.out.println("这是小明的同学");
System.out.println("他很优秀的");
}
}

代码执行如下图:

public class ExtendsShow {
public static void main(String args[]){
Father f = new Father("bob") ;
Father f1 = new Father() ;

Son s = new Son("liming") ;
Son s1 = new Son() ;

f.speak("hello") ;
f.speak() ;
f1.speak("hello") ;
f1.speak() ;
s.speak("hello") ;
s.speak() ;
s1.speak("hello") ;
s1.speak() ;
}
}

class Father {
String name = "Fater" ;

Father(String name) {
this.name = name ;
}

Father() {

}

public void speak() {
System.out.println (name+"什么都没说") ;
}

public void speak(String s){
System.out.println (name+"说:"+s) ;
}
}

class Son extends Father {
String name = "Son" ;

Son(String name){
this.name = name ;
}

Son(){

}

public void speak() {
System.out.println ("我是:"+name+"我什么都没说") ;
}

public void speak(String s){
System.out.println ("我是"+name+"说:"+s) ;
}
}