Software piracy, the illegal using, copying, and resale of applications is a major concern for anyone develops software. Software developers also worry about their applications being reverse engineered by extracting data structures and algorithms from an application and incorporated into competitor's code. A defense against software piracy is watermarking, a process that embeds a secret message in a cover software. Watermarking is a method that does not aim to stop piracy copying, but to prove ownership of the software and possibly even the data structures and algorithms used in the software. The language Java was designed to be compiled into a platform independent bytecode format. Much of the information contained in the source code remains in the bytecode, which means that decompilation is easier than with traditional native codes. In this thesis, we present a technique for watermarking Java programs by using a never-executed dummy method (Monden et.al., 2000) combined with opaque predicates (Collberg et.al., 1998; Arboit, 2002) and improved with dynamically opaque predicates (Palsberg et.al., 2000). This work presents a method to construct a dynamic opaque predicates by grouping two or more opaque predicates according to predefined rules. Any software watermarking technique will exhibit a trade-off between resilience, data rate, cost, and stealth. To evaluate the quality of a watermarking scheme we must also know how well it stands up to different types of attacks. Ideally, we would like our watermarks to survive translation (compilation, decompilation, and binary translation), optimization, and obfuscation. Add a single watermark will increasing source code approximate 3.854 bytes with dummy method that cover up to 15 characters, two dynamic data structures, two threads and two opaque predicates. Application loading-time increase approximate 6108 milliseconds.