Double Array in java programming languge

In java double Arrays are actually arrays of array.to declare a double -dimensional array variable, specifies each additional index using another set of square bracket.
Double dimensional array
a Double dimensional array can be like a table of rows and columns. 
systax:
datatype[][] variable=new datatype[n][m]
here utilize in n rows and m columns totally n *m elements in the above array.
/*
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package javaprogram;
import java.awt.*;
import javax.swing.*;
/**
 *
 * @author rajesh kumar shukla
 */
public class DoubleArray extends JApplet 
     {
     int grades[][] = { { 77, 68, 86, 73 }, { 96, 87, 89, 81 }, { 70, 90, 86, 81 } };
    
     int students, exams;
     String output;
     JTextArea outputArea;
    
     // initialize instance variables
     public void init()
         {
         students = grades.length;
         exams = grades[ 0 ].length;
        
         outputArea = new JTextArea();
         Container c = getContentPane();
         c.add( outputArea );
        
         // build the output string
         output = "The array is:\n";
         buildString();
        
         output += "\n\nLowest grade: " + minimum() +
         "\nHighest grade: " + maximum() + "\n";
        
         for ( int i = 0; i < students; i++ )
         output += "\nAverage for student " + i + " is " + average( grades[ i ] );
        
         outputArea.setFont( new Font( "Courier", Font.PLAIN, 12 ) );
         outputArea.setText( output );
     }
    
     // find the minimum grade
     public int minimum()
         {
         int lowGrade = 100;
        
         for ( int i = 0; i < students; i++ )
         for ( int j = 0; j < exams; j++ )
         if ( grades[ i ][ j ] < lowGrade )
         lowGrade = grades[ i ][ j ];
        
         return lowGrade;
     }
    
    
     // find the maximum grade
     public int maximum()
         {
         int highGrade = 0;
        
         for ( int i = 0; i < students; i++ )
         for ( int j = 0; j < exams; j++ )
         if ( grades[ i ][ j ] > highGrade )
         highGrade = grades[ i ][ j ];
        
         return highGrade;
     }
    
     // determine the average grade for a particular
     // student (or set of grades)
     public double average( int setOfGrades[] )
         {
         int total = 0;
        
         for ( int i = 0; i < setOfGrades.length; i++ )
         total += setOfGrades[ i ];
        
         return ( double ) total / setOfGrades.length;
     }
    
     // build output string
     public void buildString()
         {
         output += " "; // used to align column heads
        
         for ( int i = 0; i < exams; i++ )
         output += "[" + i + "] ";
        
         for ( int i = 0; i < students; i++ ) 
             {
             output += "\ngrades[" + i + "] ";
            
             for ( int j = 0; j < exams; j++ )
             output += grades[ i ][ j ] + " ";
         }
     }

}