long startTime=System.currentTimeMillis();     
     StringBuilder builder=new StringBuilder();
     StringBuffer buffer=new StringBuffer();

    for(int i=0;i<1000;i++){
            builder.append("Okay");}

    System.out.println("Builder Elapsed Time  :"+(System.currentTimeMillis()- 
    startTime));
    
    long bufferStartTime=System.currentTimeMillis();
    for(int i=0;i<1000;i++){
    buffer.append("Okay");}
    System.out.println("Buffer Elapsed Time  :"+(System.currentTimeMillis()- 
    bufferStartTime));
    
    OUTPUT:-
    Builder Elapsed Time:1
    Buffer Elapsed Time :0

    StringBuilder builder=new StringBuilder();
    StringBuffer buffer=new StringBuffer();
    long startTime=System.currentTimeMillis();
    for(int i=0;i<1000;i++) {
    buffer.append("Okay");
    }
    System.out.println("Buffer Elapsed Time  :"+(System.currentTimeMillis()- 
    startTime));    
    long builderStartTime=System.currentTimeMillis();
    for(int i=0;i<1000;i++){
    builder.append("Okay");}
    System.out.println("Builder Elapsed Time  :"+(System.currentTimeMillis()- 
    builderStartTime));

   OUTPUT:-
   Buffer Elapsed Time:1
   Builder Elapsed Time:0