Find Max Integer From The First N Integers of Unsorted Array Recursively in Java

Searching a sorted integer array for a specific integer is a general use-case for most of the time.

But if it is required to search an unsorted array for the first N elements in order to find the maximum element then it is required to apply a different solution.

In order to find the maximum of first N elements of an unsorted array recursively following method can be used.

package basics;

public class NumberUtils {

 public static int getMaxItemFromSubArray( int[] inArray, int index ) {
  
  if( index <= 0 || index>inArray.length )
   return -1;
  
  if ( index == 1 ) {
   return inArray[0]; 
  }
  
  int m = getMaxItemFromSubArray( inArray, index-1 ); 
  
  if ( inArray[ index-1 ] > m) {
   return inArray[ index-1 ];
  } else {
   return m;
  }
  
 }

 public static void main(String[] args) {

  int[] items = { 0, 5, 73, 33, 201, 3, 441 };
  int maxItem = getMaxItemFromSubArray( items , 0 );
  System.out.println("Max Item is = " + maxItem);  
  
  maxItem = getMaxItemFromSubArray( items , 8 );
  System.out.println("Max Item is = " + maxItem);  
  
  maxItem = getMaxItemFromSubArray( items , 3 );
  System.out.println("Max Item is = " + maxItem);  
  
  maxItem = getMaxItemFromSubArray( items , 4 );
  System.out.println("Max Item is = " + maxItem); 
  
  maxItem = getMaxItemFromSubArray( items , 5 );
  System.out.println("Max Item is = " + maxItem); 
  
  maxItem = getMaxItemFromSubArray( items , 6 );
  System.out.println("Max Item is = " + maxItem); 
  
  maxItem = getMaxItemFromSubArray( items , 7 );
  System.out.println("Max Item is = " + maxItem); 
  
 }
}

Create a NumberUtils.java file in your workspace.

When the main method inside the NumberUtils class executed it is going to print :

Max Item is = -1
Max Item is = -1
Max Item is = 73
Max Item is = 73
Max Item is = 201
Max Item is = 201
Max Item is = 441