Comments are  used to blocked any single line or multi- line code.

 Java has three kinds of comments.
 
1-Single line comments 
// single line comments are used to write comment in only single line
 single line comment begin with double forward slash
  
 2-Multi line comments 

/*multi line comment start with 
forward slash followed by astric and
end with astric followed by forward slash */

3-Document comments its begin 

/** and end /*.
  its use by the Javadoc..