Difference between StringBuffer and StringBuilder

There are many differences between StringBuffer and StringBuilder. A list of differences between StringBuffer and StringBuilder are given below: No. StringBuffer StringBuilder 1) StringBuffer is synchronized i.e. thread safe. It means two threads can't call the methods of StringBuffer simultaneously. StringBuilder is non-synchronized i.e. not thread safe. It means two threads can call the methods of StringBuilder simultaneously. 2) StringBuffer is less efficient than StringBuilder. StringBuilder is more efficient than StringBuffer. StringBuffer Example public class BufferTest{       public static void main(String[] args){           StringBuffer buffer=new StringBuffer("hello");           buffer.append("java");           System.out.println(buffer);       }   }   hellojava StringBuilder Example public class BuilderTest{       public static void main(String[] args){           StringBuilder builder=new StringBuilder("hello");           builder.append("java");           System.out.println(builder);       }   }   hellojava Performance Test of StringBuffer and StringBuilder Let's see the code to check the performance of StringBuffer and StringBuilder classes. public class ConcatTest{       public static void main(String[] args){           long startTime = System.currentTimeMillis();           StringBuffer sb = new StringBuffer("Java");           for (int i=0; i<10000; i++){               sb.append("Tpoint");           }           System.out.println("Time taken by StringBuffer: " + (System.currentTimeMillis() - startTime) + "ms");           startTime = System.currentTimeMillis();           StringBuilder sb2 = new StringBuilder("Java");           for (int i=0; i<10000; i++){               sb2.append("Tpoint");           }           System.out.println("Time taken by StringBuilder: " + (System.currentTimeMillis() - startTime) + "ms");       }   }   Time taken by StringBuffer: 16ms Time taken by StringBuilder: 0ms