Difference between String class StringBuffer class

class StringSBdiff // difference between String class StringBuffer class

{
public static void main(String[] args)
{
//String class
String s1=new String("hello");
String s2=new String("hello");
String s3=s1;
System.out.println(s1.equals(s2));
System.out.println(s1.equals(s3));

//StringBuffer class

StringBuffer sb1=new StringBuffer("hello");
StringBuffer sb2=new StringBuffer("hello");
StringBuffer sb3=sb1;
System.out.println(sb1.equals(sb2));
System.out.println(sb1.equals(sb3));


}