isSorted

public class IsSorted
{
 
  // Determine if an array is sorted in ascending order
  //
  public static boolean isSorted( int[] array )
  {
    boolean inOrder = true;
    
    // scan the list starting at index 0
    for ( int j=0; j<array.length-1 && inOrder; j++ )
    {
      // check the pair starting at j
      inOrder = array[j] <= array[j+1];      
    }
    
    return inOrder;
  }
  
  public static void main ( String[] args )
  {
    int[] values = {12, 23, -5, 56, 32, 17, -4, -49, -1, -23, 45 };
    
    // print out the array
    System.out.println("values: "); 
    for ( int val : values )
      System.out.print( val + ", " );
    
    System.out.println( );

    // determine if it is in order
    if ( isSorted(values) )
      System.out.println( "Is in order" );
    else
      System.out.println( "Is NOT in order" );

   }
}

This program that determines if an array of int is in ascending order. This is a little silly because the array is hard-coded into the program. But pretend that the array came from some external data source, perhaps from a file, and that the program needed to check that it was in order before proceeding.

The method isSorted() implements the algorithm.

For each pair of integers starting at the left:
  if any pair is out of order, the list is not in order

Each pair of integers is tested, starting with the pair at index 0 and index 1, then testing the pair at index 1 and index 2, and so on.

BUG ALERT: The last pair consists of the integers at array.length-2 and array.length-1, so the loop ending condition must test

j<array.length-1 

It is easy to forget the -1

inOrder = array[j] <= array[j+1];