Sonar CPD Detects Duplication Blocks

I did so much analysis on how cpd sonar detects duplicate blocks. But I can't figure out exactly what process is required to detect blocks or lines of code. They have a minimum number of lines.

For example, if I write like below, it doesn't detect any duplicate code, even repeating over 20 times.

        System.out.println("this is good");
        System.out.println("this is good");

        System.out.println("this is good");
        System.out.println("this is good");

        System.out.println("this is good");

        System.out.println("this is good");

        System.out.println("this is good");

        System.out.println("this is good");

        System.out.println("this is good");

        System.out.println("this is good");

      

        
        
        
      

    

Later I tried to do duplicate blocks

     try
    {
    connection = null;
    }
    catch(Exception e){
        e.printStackTrace();
    }
    try
    {
    connection = null;
    }
    catch(Exception e){
        e.printStackTrace();
    }
    try{
    connection = null;
    }
    catch(Exception e){
        e.printStackTrace();
    }
    try{
    connection = null;
    }
    catch(Exception e){
        e.printStackTrace();
    }

      

        
        
        
      

    

It is seen here as two blocks, although it has many blocks.

Please let me know the exact process that follows in this sonar overlap detection 3.4.1

In this http://docs.sonarsource.org/3.1/apidocs/src-html/org/sonar/plugins/cpd/SonarEngine.html

I found the constant block size to be 10. But I can relate this in my observation.