Getting an error! ! ! ! !

Question

1.00/5 (1 vote)

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its giving me this error and i dont know how to fix it:

Exception in thread "main" java.lang.NullPointerException
	at Testing.main(Testing.java:61)

What I have tried:

Java

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Testing 
{
	public static void main(String args[]) 
	   {
	      
		 List<String> teams = new ArrayList<String>();
		 // List<String> ghosts = new ArrayList<String>();
		 // HashMap<String, List<Integer>> map = new HashMap<String, List<Integer>>();
		  String ghoststr;
		      
		  teams.add("A");
		  teams.add("B");
		  teams.add("C");
		  teams.add("D");
		  teams.add("E");
		  
		  
		  int ghost = teams.size() % 2;
		  
		  ghoststr = "GHOST";
		  if (ghost == 1 ) 
		  {
			  
			  teams.add(ghoststr);
			  //ghosts.add("GHOST");
		  }
		  
		 //teams.add("G");
		  //teams.add("F");
		  
		  
		int totalRounds = teams.size()-1;
		int matchesPerRound = teams.size()/2;
		Game[][] rounds = new Game[totalRounds][matchesPerRound];
		//String ght = teams.get(teams.size()-1);
		
		
		for (int round = 0; round< totalRounds; round++)
		{
				
			
			for (int match = 0; match < matchesPerRound; match++) 
			{
				int home = (round + match) % (teams.size() - 1);
	            int away = (teams.size() - 1 - match + round) % (teams.size() - 1);
	            String team1 = teams.get(home);
		        String team2 = teams.get(away);
		        
	            if (match == 0)
	            {
	            	away = teams.size()-1;
	            	
	            }
	            
	            
	            	//if ( team1 != team2)
	             rounds[round][match].team1= team1; 
	             rounds[round][match].team2 = team2;
		       //rounds[round][match] = Game.team1 + " v " + team2 ;		
	            	
	            	
	            
	            
			}
		}
		
		
		
		 for (int i = 0; i < rounds.length; i++) {
			 for(int j = 0; j < rounds.length ; j++)
			 {
				 System.out.println("Round " + (i + 1));
				 if ( !(rounds[i][j].team1.equals(ghoststr) || rounds[i][j].team2.equals(ghoststr)) )
		         {
					String printstr = rounds[i][j].team1 + "V" + rounds[i][j].team2;
					System.out.println(printstr);
					System.out.println();
		         }
				
				 
			 }
	         
	     }

				
				}

}
class Game 
{
	String team1;
	String team2;
}

Posted 5-Apr-17 23:46pm

Member 13110105

Updated 6-Apr-17 0:31am

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Comments

CHill60 6-Apr-17 5:54am

Is the line giving the error rounds[round][match].team1= team1;?

Member 13110105 6-Apr-17 6:04am

yes

CHill60 6-Apr-17 6:17am

Then I suspect you have not set rounds[round][match] to an instance of the Games object.
I suspect you need a line similar to rounds[round][match] = new Game;

Member 13110105 6-Apr-17 6:24am

Thank you but now the if statement in the code below is giving me a problem:

for (int i = 0; i < rounds.length; i++) {
for(int j = 0; j < rounds.length ; j++)
{
System.out.println("Round " + (i + 1));
if ( !(rounds[i][j].team1.equals(ghoststr) || rounds[i][j].team2.equals(ghoststr)) )
{
String printstr = rounds[i][j].team1 + "V" + rounds[i][j].team2;
System.out.println(printstr);
System.out.println();
}

}

}

the error is :

java.lang.ArrayIndexOutOfBoundsException: 3
at Testing.main(Testing.java:78)

CHill60 6-Apr-17 6:28am

You have run off the end of the array by the sound of it. Debug and check the values of i, j and rounds.length

Member 13110105 6-Apr-17 6:42am

is there away to fix it? if yes how?

CHill60 6-Apr-17 7:00am

Make sure your indexes i and j stay within the bounds of the array.
You might need to refresh your knowledge of Arrays[^]

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CHill60 · Accepted Answer · 2017-04-06T00:31:00

Solution 1

From comments.

OP had declared the array but had not created new instances of the object when populating it.

Something similar to this was needed:

rounds[round][match] = new Game;
rounds[round][match].team1= team1; 
rounds[round][match].team2 = team2;

Posted 6-Apr-17 0:31am

CHill60

Updated 6-Apr-17 0:32am

v4