Garbage collection as a memory management technique has been around a long time, but in Java it took on a new life. In languages such as C++, memory must be managed manually, with the programmer explicitly releasing unused objects. This is a source of problems because it is common to forget to release a resource after it is no longer needed, or to release a resource that is still being used. Java prevents these problems by managing memory for you. This can be done in an efficient manner because all objects in Java are accessed through a reference. Thus, when the garbage collector finds an object to which there is no reference, it knows that the object is unused and can be recycled. Had Java allowed objects to be operated on directly (in a fashion similar to the simple types), then such an efficient means of garbage collection would not have been possible.

Java’s use of garbage collection reflects the philosophy of Java in general. The Java designers took great pains to create a language that would prevent some of the problems typical of other programming languages. By using garbage collection, it is not possible for the programmer to forget to release a resource or to mistakenly release a resource that is still in use. Thus, garbage collection heads off an entire class of problems.

Remember: this is chapter one of The Art of Java, by Herbert Schildt and James Holmes (McGraw-Hill/Osborne, ISBN 0-07-222971-3, 2003). Check it out at your favorite bookstore today.   Buy this book now.