The Java Course provides a general introduction to programming in Java. It is based on A.B. Downey's book, How to Think Like a Computer Scientist. Click here for details.

Arrays and Objects

In many ways, arrays behave like objects:

  • When you declare an array variable, you get a reference to an array.
  • You have to use the new command to create the array itself.
  • When you pass an array as an argument, you pass a reference, which means that the invoked method can change the contents of the array.

Some of the objects we have looked at, like Rectangles, are similar to arrays, in the sense that they are named collection of values. This raises the question, "How is an array of 4 integers different from a Rectangle object?"

If you go back to the definition of "array" at the beginning of the chapter, you will see one difference, which is that the elements of an array are identified by indices, whereas the elements (instance variables) of an object have names (like x, width, etc.).

Another difference between arrays and objects is that all the elements of an array have to be the same type. Although that is also true of Rectangles, we have seen other objects that have instance variables with different types (like Time).

Last Update: 2011-01-24