Homework 4, MON WED class:assigned MON OCT 22 due TUE OCT 30 at 11:59pm
TUE THUR class: assigned TUE OCT 23 due WED OCT 31 at 11:59pm

4a. Write a program in which the main method calls a method with the heading public static char changeCase(char ch) that if ch is a lowercase letter, the method will return the corresponding uppercase letter, and if ch is a uppercase letter, the method will return the corresponding lowercase letter. If ch is not a letter, the method returns the same value of ch. Thus, for instance, changeCase('a') returns A, changeCase('B') returns b, and changeCase('3') returns 3. Note that the uppercase letters have a unicode (ascii code) value that is 32 lower than the corresponding lowercase ones.

Your main method should contain three calls to changeCase() one for each case mentioned above, e.g.,
System.out.println(changeCase('a') )
System.out.println(changeCase('B') )
System.out.println(changeCase('3') )

4b. Write a method public static char toUpperCase(char ch) that if ch is a lowercase letter, the method will return the corresponding uppercase letter, and if ch is any other character, it will return that character. Assign the string consisting of "My country tis of thee, Sweet land of liberty, Of thee I sing" to the variable s and using toUpperCase() in a loop, convert the entire string to uppercase letters.