本次项目是：以面向对象的思想设计动物乐园系统。 动物乐园中有猫，鸭子等成员，还可以增加新成员。 猫和鸭子都有自己的名字，都有自己的腿，但腿的条数不同，猫和鸭子会发出叫声，猫的叫声是：喵喵喵……,鸭子的叫声是;嘎嘎嘎……

public abstract class animal {

protected String name;

public animal(String name) {

super();

this.name = name;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public abstract void show();

}

---------------------------------2

public interface lu {

public int leg();

}

-------------------------3

public class cat extends animal implements lu{

private int leg;

public cat(String name, int leg) {

super(name);

this.leg = leg;

}

public int getLeg() {

return leg;

}

public void setLeg(int leg) {

this.leg = leg;

}

---------------------------------------------4

public class duck extends animal implements lu {

private int leg;

public duck(String name, int leg) {

super(name);

this.leg = leg;

}

public int getLeg() {

return leg;

}

public void setLeg(int leg) {

this.leg = leg;

}

@Override

public void show() {

// TODO Auto-generated method stub

System.out.println("嘎");

}

@Override

public int leg() {

return this.leg;

}

}

------------------5

public class hai extends animal {

public hai(String name) {

super(name);

}

@Override

public void show() {

System.out.println("海豚");

}

}

---------------

public class test {

private static Object lu;

/**

* @param args

*/

public static void main(String[] args) {

// TODO Auto-generated method stub

animal[] a=new animal[3];

a[0]=new cat("小猫",4);

a[1]=new duck("鸭子",2);

a[2]=new hai("海豚");

System.out.println("动物的名字"+"\t"+"腿数"+"\t\t"+"动物叫");

for(int i=0;i<a.length;i++)

{

if(a[i] instanceof lu)

{

String name=a[i].getName();

int legnum=((lu)a[i]).leg();

//System.out.println(name+ "\t\t" +legnum+ "\t\t");

System.out.print(name + "\t\t" + legnum + "\t\t");

a[i].show();

}

else

{

String name=a[i].getName();

System.out.print(name+ "\t\t" +0+ "\t\t");

a[i].show();

}

}

}

}