Java Array Variables

Java Array Variables

• An array is a special type of object that can hold a collection of equal elements.
• Type of the elements of the array is called the base type of the array.
• The number of elements an array contains, is a fixed attribute called its length.
• Java supports arrays that can contain any primitive types or reference types.
• We can create an array of a specified length, or access the elements with the index operator, [ ].
• We first declare a variable of the appropriate type and then use the new operator to create an instance of it.
  Array defining examples:

  ...
   int [] arrayOfInts;  // preferred
   int arrayOfInts [];  // C-style and ok
   String [] someStrings;
  
   arrayOfInts = new int [42];
   arrayOfInts[0]=23;
   someStrings = new String [number + 2];
   someStrings [1] = "Boofa";
  ...

• Java supports C-style curly braces {} to construct the initialized values for an array.
  Array with initializing examples:

  ...
  int [] primes = { 1, 2, 3, 5, 7, 7+4 }; // e.g., primes[2] = 3 
  String [] verbs = { "run", "jump", someWord.toString(  ) };
  Button [] controls={stopButton, new Button("Forwards"), new Button("Backwards")};
  // All types are subtypes of Object
  Object [] objects = { stopButton, "A word", null };
  ...

• You can create a multidimensional array using multiple bracket pairs, one for each dimension.
  Multidimensional Array defining examples:

  ...
    ChessPiece [][] chessBoard;
    chessBoard = new ChessPiece [8][8];
    chessBoard[0][0] = new ChessPiece.Rook;
    chessBoard[1][0] = new ChessPiece.Pawn;
  ...

• Of course, you can create arrays with more than two dimensions.
  Here are some examples:

  ...
   byte[][] smallArray = { { 10, 11, 12, 13 }, { 20, 21, 22, 23 },
          { 30, 31, 32, 33 }, { 40, 41, 42, 43 } };
   Object events[][] = { { new Integer(1452), new String("Italy") },
          { new Integer(1472), new String("b.jpg") },
          { new Integer(1483), new String("Hr") },
          { new Integer(1495), new String("Pte") },
          { new Integer(1503), new String("m.jpg") },
          { new Integer(1519), new String("F") } };
  ...