Answers for "java why stringbuilder"

string builder 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.  

StringBuilder builder = new StringBuilder("Harvard"); 
// mutable you modify object new keyword ile olusturuoyrsun StringBuilder
        builder.append(" School"); 
// append method we are calling from Builder 
//** it is not synchronized means fast
        System.out.println(builder); // Harvard School

stringbuilder in java 8

public StringBuilder reverse()