Lab 4: Conditionals & Stack Diagrams

Objectives

The main goals for this lab are:

  1. Practice drawing stack diagrams.

  2. Practice reading code and evaluating logical expressions.

1. Stack Diagrams

For each of the follow programs, draw a stack diagram to trace out what happens as the program executes.

1.1 Add

class Add {
  public static int add(int a, int b) {
    int result = a + b;
    return result;
  }

  public static void main(String[] args) {
    int a = 4;
    int b = 8;
    int c = add(b, a);
    System.out.println(a + " + " + b + " = " + c);
  }
}

Draw the stack diagram below.

1.2 Add2

class Add2 {
  public static int add(int a, int b) {
    a = 2;
    int result = a + b;
    return result;
  }

  public static void main(String[] args) {
    int a = 4;
    int b = 8;
    int c = add(a, b);
    System.out.println(a + " + " + b + " = " + c);
  }
}

Draw the stack diagram below.

TODO: Show Prof. Shiptoski your work before continuing on to the next section. ---

2. Expressions

For each expression, write down the value of the expression, and the date type of the expression.

int x = 5;
int y = 13;
int z = 15;
String message = "cat!";
boolean Done = false;

1: (x < 10) && (y < 10)

Answer:

2: (x < 10) || (y < 10)

Answer:

3: (x < 10) && (x > 0)

Answer:

4: (x > 10) || (x < 0)

Answer:

5: (5 / x) > 7.0

Answer:

6: (z / 2) > 7.0

Answer:

7: message.compareTo(“cats”) == 0

Answer:

8: !Done

Answer:

9: Done || (x < 6 && y > 10)

Answer:

TODO: Show Prof. Shiptoski your work before continuing on to the next section.

3. Colors

Consider the following code.

String colorName = "purple";

if (colorName.compareTo("red") != 0) {
  System.out.println(colorName + " is not primary");
} else if (colorName.compareTo("blue") != 0 {
  System.out.println(colorName + " is not primary");
} else if (colorName.compareTo("yellow") != 0) {
  System.out.println(colorName + " is not primary");
} else {
  System.out.println(colorName + " is primary");
}

1: What does the above code print out when colorName = "purple"?

Answer:

2: What does the above code print out when colorName = "red"?

Answer:

3: What does the above code print out when colorName = "yellow"?

Answer:

TODO: Show Prof. Shiptoski your work and then you are all done with lab 4.