Java is a computer programming language that is class-based, object-oriented, java is, as of 2013, one of the most popular programming languages in use. The Java Development Kit (JDK) is an implementation of java language, which consists of a Java Virtual Machine and all of the java class libraries. There are thousands of classes in the java class libraries, and there are many kinds of relationships between classes. In this paper, we use complex network theory to study the topology of the java class libraries, according to analyzing to the networks feature characters, important classes and interfaces in java class libraries are found, we hope to find the relationship between the characters of complex networks and software reliability.