Lab 2, 

Task 1.2.4
----------

1) s2.substring(0, 3)

2) s2.toUpperCase().substring(0, 3)

   *or*

   s2.substring(0, 3).toUpperCase()

3) s2.charAt(3)

4) possible answers include:

   s1.toUpperCase().substring(2) + s2.toUpperCase().charAt(4) 

Task 1.2.5
----------

    /*
     * replaceStart - takes s1 and s2 and creates a new string in which
     * the first s1Len characters of s2 are replaced by s1,
     * where s1Len is the length of s1.
     */

    public static String replaceStart(String s1, String s2) {
        int s1Len = s1.length();
        if (s1Len < s2.length()) {
            String s2End = s2.substring(s1Len);  // in Python: s2[s1Len: ]
            s1 += s2End;
        }

        return( s1 );
    }

Task 1.2.6
----------
The method replaceStart returns the string, however, to display
the string we call the method from with the System.out.println statement.

An alternative may be:

String str = replaceStart("hello", "bye");
System.out.println( str );