Who can solve this difficult problem?

Question

I have written a java program:
import java.util.*;
class Test0 {
public static void main(String[] args) {
LinkedList[] Cate= new LinkedList[4];
(Cate[0]).add(0,"cat");
(Cate[0]).add("kate");
System.out.println(Cate[0]);
Cate[2].add("dog");
Cate[2].add("girl");
for(int i=0;i<4;i++){
Cate.add("boy");
System.out.println(Cate[i]);
} // end of main class
// end of class
But i can not run it correctly,why?

Answer 1

No, I can not compile it correctly:
import java.util.*;
class Test0 {
public static void main(String[] args) {
class Point{
public int x=2;
public int y=5;
LinkedList[] Cate= new LinkedList[4];
// according your advice:
for(int i=0;i<4;i++){
Cate = new LinkedList();
Point x1 = new Point();
Point x2 = new Point();
Cate[0].add(x1);
Cate[0].add(x2);
Cate[2].add("dog");
Cate[2].add("girl");
System.out.println( ((Point)(Cate[0].get(0)) ).x );
System.out.println( ((Point)(Cate[0].get(0)) ).y );
System.out.println( ((Point)(Cate[0].get(1)) ).x );
System.out.println( ((Point)(Cate[0].get(1)) ).y );
for(int i=0;i<4;i++){
//Cate.add("boy");
System.out.println(Cate[i]+" "+Cate[i].size() );
I got this:
[xwl@zhyj_12 Test.old]$ javac Test0.java
Test0.java:13: incompatible types
found : java.util.LinkedList
required: java.util.LinkedList[]
Cate = new LinkedList();
^
1 error
But Ragnvald told me another method yestoday,it works perfectly, And I appreciate him. His code like this:
import java.util.*;
class Test0 {
public static void main(String[] args) {
class Point{
public int x=2;
public int y=5;
LinkedList[] Cate= new LinkedList[4];
// The difference is Cate or Cate[i] !!!!
for(int i=0;i<4;i++){
Cate[i] = new LinkedList();
Point x1 = new Point();
Point x2 = new Point();
Cate[0].add(x1);
Cate[0].add(x2);
Cate[2].add("dog");
Cate[2].add("girl");
System.out.println( ((Point)(Cate[0].get(0)) ).x );
System.out.println( ((Point)(Cate[0].get(0)) ).y );
System.out.println( ((Point)(Cate[0].get(1)) ).x );
System.out.println( ((Point)(Cate[0].get(1)) ).y );
for(int i=0;i<4;i++){
//Cate[i].add("boy");
System.out.println(Cate[i]+" "+Cate[i].size() );