string buffer or builder for long output string code example

Example 1: stringbuffer vs stringbuilder java

The StringBuffer and StringBuilder class both produces mutable string objects.
 The main difference between them is that StringBuffer is thread safe;
 StringBuilder is not thread safe.

Example 2: difference between string vs stringbuffer

The main similarity between String and StringBuffer class is that both are 
thread safe.
The main difference is that String is immutable; StringBuffer is mutable.