why?
package zh.codegym.task.task06.task0621;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
/*
猫之间的关系
*/
public class Solution {
public static void main(String[] args) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String gfName = reader.readLine();
Cat catGF = new Cat(gfName);
String gmName = reader.readLine();
Cat catGM = new Cat(gmName);
String fName = reader.readLine();
Cat catF = new Cat(fName,null,catGF);
String mName = reader.readLine();
Cat catM = new Cat(mName,catGM,null);
String sName = reader.readLine();
Cat catS = new Cat(sName,catM,catF);
String dName = reader.readLine();
Cat catD = new Cat(dName,catM,catF);
System.out.println(catGF);
System.out.println(catGM);
System.out.println(catF);
System.out.println(catM);
System.out.println(catS);
System.out.println(catD);
}
public static class Cat {
private String name;
private Cat mother;
private Cat father;
Cat(String name) {
this.name = name;
}
Cat(String name, Cat mother, Cat father) {
this.name = name;
this.mother = mother;
this.father = father;
}
@Override
public String toString() {
if (mother == null){
if(father == null){
return "猫的名字为" + name + ", 无母亲, 无父亲";
}
else{
return "猫的名字为" + name + ", 无母亲, "+ father.name+"是父亲";
}
}
else{
if(father == null){
return "猫的名字为" + name + ", " + mother.name + "是母亲, 无父亲";
}
else{
return "猫的名字为" + name + ", " + mother.name + "是母亲, "+ father.name+"是父亲";
}
}
}
}
}