how to make a stringbuilder in java code example

Example: stringbuilder in java

Java StringBuilder class is used to create
  mutable (modifiable) string. The Java
  StringBuilder class is same as StringBuffer
  class except that it is non-synchronized.
    
StringBuilder()
    creates an empty string Builder with the initial capacity of 16.
StringBuilder(String str)
    creates a string Builder with the specified string.
StringBuilder(int length)
    creates an empty string Builder with the specified capacity as length.