Check If An Array Is Sorted In Java

In this tutorial, we will see a Java program to check if an array is sorted in Java.

Introduction

We will write a Java program to check if the array is sorted or not.

We will take a sample integer array arr = {1, 3 , 5, 9}; We will return true if the array is sorted or false if the array is not sorted.

Check if an array is sorted or not in Java

/**
 * A Java program to check if the array of integers is sorted
 * or not using for loop iteration.
 * 
 * @author coderolls.com
 *
 */
public class SortedArrayTester {

  public static void main(String[] args) {
    int[] arr = {2, 5, 9, 8, 11, 18, 13};
    
    boolean isSorted = isArraySorted(arr);
    
    //Use this to check the sorted case
    
    /*
    * int[] arr2 = {2, 5, 9, 11, 18};
    * boolean isSorted = isArraySorted(arr2);
    */
    if(isSorted) {
      System.out.println("The array is sorted.");
    }
    else {
      System.out.println("The array is not sorted.");
    }
  }
  
  private static boolean isArraySorted(int[] arr) {
    int n = arr.length;
    
    for(int i=0; i<n-1; i++) {
      //in a sorted array current number should be 
      //always less than the next number in the array
      if(arr[i]>arr[i+1]) {
        return false;
      }
    }
    return true;
  }
}

Output:

The array is not sorted.

Explanation:

1. In the main method we are taking a sample array arr and passing it to the isArraySorted() method to check if the array is sorted or not. This method returns a boolean value. true - if an array is sorted, false - if an array is not sorted
2. In the isArraySorted() method, we are iterating over an array from index 0 to n-1, (n-length of the array) and we will check if the current number (number at index i) is greater than the next number ( number at index i+1).
3. If the current number (number at index i) is greater than the next number ( number at index i+1), that means the array is not sorted, and we will return false.
4. If the control came out of the for loop, that means the array is sorted and we will return true.
5. When we receive the boolean result isSorted we will print the output.

Conclusion

we can check if the primitive arrays are sorted or not by comparing the adjacent array elements.

The example Java programs used in the above article can be found at this GitHub repository, blogpost-coding-examples/java-programs/second-largest-element-in-an-array/.

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