Scramble Words Besides First and Last Chars

I have been trying to figure out how to scramble the words in between 1st and last letters. All I have some up with is this for loop for iterating through the input.

Scanner in = new Scanner(System.in);

  while(in.hasNext()){
    String str = in.next();
    System.out.println(str);
  }

    }

public void scrambler(String str){

//shuffle letters in word besides first and last 
        for(int i =0; i < str.length(); i++){


        }
    }