How to empty a StringBuffer

We know that StringBuffer is reusable , We may want to empty a String Buffer ( lets say at end of a loop )
so how do you do it ?

The easiest way i came across use the method setLength()

public void setLength(int newLength)

You may have the case like
StringBuffer sb = new StringBuffer("HelloWorld")
// after many iterations and manipulations
sb.setlength(0);
// reuse sb

Please note you cant say
StringBuffer sb = "";
You will get a type mismatch error saying that "Cannot assign a value of type String to StringBuffer"
Makes sense as StringBuffer is not String , and they both inherit from java.lang.Object