CS 140 - Exam 2 Study Guide

1. Make sure that you can write methods to do all of the following operations on pictures: flipHorizontal, flipVertical, rotateLeft, rotateRight, shrink, and enlarge. Make sure that you can open a picture and call these from the main method.
2. Write a Java code segment that prompts for and reads an integer from the user and prints yes if the number is divisible by 173 or not.
3. Write a Java code segment that prompts for and reads an integer from the user and prints yes if the number is between 70 and 100, and no if it is not.
4. Write a Java code segment that prompts for and reads an integer x from the user and prints x asterisks on the console.
5. Write a Java code segment that determines the largest value of three integer variables, x, y, and z.
6. Write a complete Java program that uses a for loop to read ten integers from the user and computes the average of the integers.
7. Write a complete Java program that allows the user to choose two colors from an RGB color pallette (hint use ColorChooser.pickAColor()) and prints out the distance between those two colors.
8. Write a Java expression to generate a random integer between -180 and 180 inclusive and store the integer in the variable x. Inclusive means you should include -180 and 180 as values.
9. Write a Turtle method named colorfulCircle() causes a turtle to turn in a circle and that, when every time it moves, changes its pen color to a random color.
10. Assume a, b, and c are integer variables. If there is something wrong with the statements below indicate what the problem is.

       a) if a > b {
             c = b;
          }
           
       b) if (a > b) {
             c = b
          } 
          
       c) if (a > b {
             c = b;
             System.out.println("a is bigger than b");
          }
          else 
          
       d) if (a > b) { c = b; } 
    

11. The operator ! is logical negation. So !true is the same as false and !false is true. The precedence of &&, ||, and ! is that && has the highest precedence, then ||, and then !. As an example consider the expression below:

      int x = 5;
      int y = 7;
      System.out.println( x > y || !(3 > 4) && 5 <= 6 );
    

    The first condition checked is if x > y. This is false. Next we check if !(3 > 4). This is true, 3 is not greater than 4. Now we check if 5 is less than 6. This is true. Both sides of && are true so it evaluates to true.

    Assuming that x is 1 What is the output of the following:

        int x = 1;
        System.out.println((true) && (3 > 4));
        System.out.println(!(x > 0) && (x > 0));
        System.out.println((x > 0) || (x < 0));
        System.out.println(x != 0 || x == 0);
        System.out.println(x >= 0 || x < 0);
        System.out.println((x != 1) == !(x == 1));
    	

12. What is the output of the following code? Try and figure it out by thinking it through. Verify your answer by cutting and pasting it into a program.

      int x = 3;
      int y = 2;
      int z = 0;
      
      if (x > 2) {
        if (y > 2) {
           z = x + y;
           System.out.println("z is " + z);
        }
      }
      else {
        System.out.println("x is " + x);
      }
    

13. In the above question what is the output if x is 3 and y is 4?
14. In the above question what is the output if x is 2 and y is 2?
15. Print the numbers from 1 to 100 that are divisible by 3 or 11.
16. Study the code segment below and figure out what it does without running it.

        World w = new World();
        Turtle t = new Turtle(w);
        
        t.penUp();
        t.moveTo(w.getWidth(),w.getHeight());
        t.turnToFace(0,0);
        t.penDown();
        int v = 0;
        for (int i = 0; i < 500; i++) {
           t.forward(2);
           v = (v + 1) % 256;
           t.setPenColor(new Color(v,v,v));
        }