Separate the construction of a complex object from its representation so that the same construction process can create different representations.

Use the Builder pattern when

• the algorithm for creating a complex object should be independent of the parts that make up the object and how they're assembled
• the construction process must allow different representations for the object that's constructed

• java.lang.StringBuilder
• java.nio.ByteBuffer as well as similar buffers such as FloatBuffer, IntBuffer and so on.
• java.lang.StringBuffer
• All implementations of java.lang.Appendable
• Apache Camel builders

• Design Patterns: Elements of Reusable Object-Oriented Software
• Effective Java (2nd Edition)