How can I copy a 2d array to a new and bigger one with eye for adding more items in the new one while still having the original data? My code makes out of bounds failure - what is my mistake? I try to say that the copy array should be original array.length x - but doesn't work.

import java.util.Scanner; // import scanner to the program

public class TestTest {

// Declaring Scanner object.

public static Scanner userInput = new Scanner(System.in); 

public static void main(String[] args) {
    
    // Variables
    
     int number = 1;
     
    // Declaring 2d Array
     
     int[][] myArray = new int [3][3];
     
     // Loop values into the array
     
     for(int i =0; i<myArray.length; i  ) 
     {
         myArray[i][0]= number;
         number  ;
         
         myArray[i][1]= (int) (Math.random () * 10)  1;
         myArray[i][2]= (int)(Math.random() * ((1000 - 100)   1))   100;         
         
     }
     
     // Print the original array
     
     System.out.println("This is original array:");
     
     for(int i =0; i<myArray.length; i  ) 
     {
         
         
      System.out.println(myArray[i][0] " "   myArray[i][1] " "  myArray[i][2]);
             
         
     }
     
     // Make a copy of the original array and expand the length with 3.
     
      int[][] copyArray =new int[myArray.length 3][3];
      
      for (int i = 0; i < copyArray.length;   i) 
      {
        copyArray[i] = new int[myArray[i].length];
         
        
         for (int j = 0; j < copyArray[i].length;   j) 
         {
            copyArray[i][j] = myArray[i][j];
         }
         
      }
      
     
     
      
      
      // Print the copy
      
      System.out.println("This is the copy:");
      
      
      for (int i = 0; i < copyArray.length 3;   i) 
      {
          
        System.out.println(copyArray[i][0] " "   copyArray[i][1] " "  copyArray[i][2] ); 
          
         
      
      }
      
      
      
      
      
      
      
      
      
 

}

}

CodePudding user response：

You're getting ArrayIndexOutOfBounds because array copyArray has greater length than your source array myArray.

Therefore, when index i exceeded the length of the source array, this line would cause an exception:

copyArray[i] = new int[myArray[i].length];

Because there would be no nested array referred by myArray[i].

CodePudding user response：

Try it like this

int[][] copyArray =new int[myArray.length 3][3];
      
for (int i = 0; i < myArray.length;   i) { // length of myArray
    
    copyArray[i] = new int[myArray[0].length]; // 0 instead of i
    
    for (int j = 0; j < myArray[i].length;   j) { // length of myArray
       copyArray[i][j] = myArray[i][j];
    }      
}

Also since copyArray has already increased size you don't need the 3 in the last for loop. Hope I helped, good luck