PASSING ARRAYS TO A METHOD

PASSING A ONE-DIMENSIONAL ARRAY TO A METHOD

• A single array element is passed to a method by value, the same as any primitive variable. Only a copy of the element is made, and the method does not alter the value of the element directly.
  Example
  public class Test
  { public static void main(String[ ] args)
     { double grades[ ] = {85.0,  67.0, 90.0};
        display(grades[2]);
        System.out.println(grades[2]);
      }
      public static void display(int x)
     {  x = x + 10.0;
        System.out.println(x);
      }
  }
  Output
  100.0
  90.0

• An entire array is passed to a method by reference, so the method may directly modify elements of the array.Because an array is an object, when the entire array is passed as a parameter, a copy of the reference to the original array is passed. The method can change an element of the array permanently because it is referring to the original element value.
  Example
  public class Test
  { public static void main(String[ ] args)
     { double grades[ ] = {85.0,  67.0, 90.0};
        add10(grades);
        for(i =0; i <grades.length; i++)
        System.out.println(grades[i] + "  " );
      }
      public static void add10(double [ ]  x)
     {  for(int i =0; i < x.length;i++)
        { x[i] = x [i] + 10.0;
         }
      }
  }
  Output
  95.0  77.0  100.0

RETURNING ONE-DIMENSIONAL ARRAY FROM THE METHOD

A method can return an one-dimensional array.

Syntax:  return  arrayname;

Example

class Test
{ public int [ ] getArray( )
  {int array[ ] = {1,8,5};
    return array;
  }
}

public class TestArray
{ public static void main(String[ ] args)
   { Test  x = new Test( );
      int  y[ ] = x.getArray( );
    }
}

PASSING A TWO-DIMENSIONAL ARRAY TO A METHOD

• A single array element is passed to a method by value, the same as any primitive variable. Only a copy of the element is made, and the method does not alter the value of the element directly.
  Example
  public class Test
  { public static void main(String[ ] args)
    { double grades [3][4] = { { 45.0, 89.0, 90.0, 67.0}, { 54.0, 75.0, 34.0, 99.0}, {88.0, 92.0, 10.0, 56.0} };
       display(grades[2][1]);
     }
    public static void display(double d)
    { System.out.println (d);
     }
  }
• An entire array is passed to a method by reference, so the method may directly modify elements of the array.Because an array is an object, when the entire array is passed as a parameter, a copy of the reference to the original array is passed. The method can change an element of the array permanently because it is referring to the original element value.

        Example
        public class Test
       { public static void main(String[ ] args)
       { double grades [3][4] = { { 45.0, 89.0, 90.0, 67.0}, { 54.0, 75.0, 34.0, 99.0}, {88.0, 92.0, 10.0, 56.0} };
         display(grades);
       }
        public static void display(double g[3][4])
       {   for (int row =0; row <g.length; row++)
               { for (int col = 0; col <g[row].length; col++)
                    { System.out.println(g[row][col] + "   ");
                     }
                      System.out.println( );
                 }
       }
      }

RETURNING TWO-DIMENSIONAL ARRAY FROM THE METHOD

A method can return a two-dimensional array.

Syntax:  return  arrayname;

Example 
class Test
{ public double [ ] [ ] getGrades( )
  {double grades [3][4] = { { 45.0, 89.0, 90.0, 67.0}, { 54.0, 75.0, 34.0, 99.0}, {88.0, 92.0, 10.0, 56.0} };
    return grades;
  }
}

public class TestArray
{ public static void main(String[ ] args)
   { Test  x = new Test( );
      double  y[ ][ ]  = x.getGrades( );
    }
}