Arrays

• A Java array behaves like a class.

• Every array has an instance variable called length that specifies how big the array is.

• Note that this is the maximum size of the array, not the number of elements being used.

• To use an array, you must:
  
  
  1. declare a variable to hold the array

  2. create the array (allocate the space for the slots in the array with new).

  3. create the elements in the array and store values in the array (allocate the space for the elements with new).
  
  
• When you declare an array, you use brackets, and they may be after the class or after the identifier name:

  String		array1[];
  String[]	array2;
  

  
  
• Next, you must create the slots with new:

  array1 = new String[99];	// 99 slots, 99 references, each set to null
  

  
  
• Next, you must allocated each object in the array with new again:

  array1[0] = new String("Cathy");
  array1[1] = new String("Pippi");
  array1[2] = new String("Lenny");
  

• Note: null means an null reference (and does not evaluate to 0 or '\0'.)

• Like C and C++, arrays start at index 0.

• An array stores references to objects, it does not store the objects themselves.

• The C equivalent is that arrays in Java are arrays of pointers.

• Since primitives don't have constructors, you don't use the new in the third step - just assign the values.

• Again, Strings are special, so you don't necessarily have to do the 3 steps, but it's a good idea to practice it so you do it correctly for other classes.

• You may want to draw the memory involved with your array programming assignment.