Java program to check array bounds while inputting array elements

An array is a linear data structure used to store groups of elements with similar data types. It stores data in a sequential manner. Once we create an array, we cannot change its size, i.e. it is fixed length.

This article will help you understand the basic concepts of arrays and array binding. Also, we will discuss the java program to check the bounds of an array while inputting elements into the array.

Arrays and array binding

We can access array elements by index. Suppose we have an array of length N, then

In the above picture we can see that there are 7 elements in the array, but the index values ​​are from 0 to 6, that is, 0 to 7 - 1.

The range of an array is called its boundary. The range of the above array is from 0 to 6, therefore, we can also say that 0 to 6 are the bounds of the given array. If we try to access an out-of-range index value or a negative index, we will get an ArrayIndexOutOfBoundsException. This is an error that occurs at runtime.

Syntax for declaring arrays

Data_Type[] nameOfarray; 
// declaration
Or,
Data_Type nameOfarray[]; 
// declaration
Or,
// declaration with size
Data_Type nameOfarray[] = new Data_Type[sizeofarray]; 
// declaration and initialization
Data_Type nameOfarray[] = {values separated with comma};

We can use any of the above syntax in our program.

Checking array bounds when entering elements into an array

Example 1

If we access elements within the range of the array, then we will not get any error. The program will execute successfully.

public class Main {
   public static void main(String []args) {
      // declaration and initialization of array ‘item[]’ with size 5
      String[] item = new String[5]; 
      // 0 to 4 is the indices 
      item[0] = "Rice";
      item[1] = "Milk";
      item[2] = "Bread";
      item[3] = "Butter";
      item[4] = "Peanut";
      System.out.print(" Elements of the array item: " );
      // loop will iterate till 4 and will print the elements of ‘item[]’
      for(int i = 0; i <= 4; i++) {
         System.out.print(item[i] + " ");
      }
   }
}

Output

Elements of the array item: Rice Milk Bread Butter Peanut

Example 2

Let us try to print values ​​outside the range of the given array.

public class Tutorialspoint {
      public static void main(String []args) {
      String[] item = new String[5];
      item[0] = "Rice";
      item[1] = "Milk";
      item[2] = "Bread";
      item[3] = "Butter";
      item[4] = "Peanut";
      // trying to run the for loop till index 5
      for(int i = 0; i <= 5; i++) {
         System.out.println(item[i]);
      }
   }
}

Output

Rice
Milk
Bread
Butter
Peanut
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 5 out of bounds for length 5
at Tutorialspoint.main(Tutorialspoint.java:11)

As we discussed before, if we try to access an array with an index value that is outside its range or a negative index, we will get an ArrayIndexOutOfBoundsException.

In the above program, we tried to execute a for loop until index 5 of the array "item[]", but its range is only 0 to 4. So after printing the elements till 4 we get the error.

Example 3

In this example, we try to handle ArrayIndexOutOfBoundsException using try and catch blocks. We will check the array bounds when the user enters elements into the array.

import java.util.*;
public class Tutorialspoint {
   public static void main(String []args) throws ArrayIndexOutOfBoundsException {
      // Here ‘sc’ is the object of scanner class
      Scanner sc = new Scanner(System.in); 
      System.out.print("Enter number of items: ");
      int n = sc.nextInt();
      // declaration and initialization of array ‘item[]’
      String[] item = new String[n]; 
      // try block to test the error
      try {
         // to take input from user
         for(int i =0; i<= item.length; i++) {
            item[i] = sc.nextLine();
         }
      }
      // We will handle the exception in catch block
      catch (ArrayIndexOutOfBoundsException exp) {
         // Printing this message to let user know that array bound exceeded
         System.out.println(
         " Array Bounds Exceeded  \n Can't take more inputs ");
      }
   }
}

Output

Enter number of items: 3

in conclusion

In this article, we learned about arrays and array binding. We have discussed why we receive an error if we try to access an array element beyond its scope and how to handle this error using try and catch blocks.

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