8.9. Additional Practice Exercises

8.9.1. Code Tracing

Code Tracing

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Note

The objective of the following exercises is for students to understand how nodes are created and linked in memory using the Node class. They should be able to trace references step by step to predict program output and recognize that next can be reassigned.

Question 1

Draw the memory map for the following code:

Node n1 = new Node("A");
Node n2 = new Node("B");
n1.setNext(n2);

Sample Visualizations

Note: The debugger breakpoint is on line 5.

Note: The debugger breakpoint is on line 6.

Note: The debugger breakpoint is on line 7.

Question 2

Draw the memory map for the following code and write the output given in the final line.

Node x = new Node("X");
x.setNext(new Node("Y"));
x.getNext().setNext(new Node("Z"));

System.out.println(x.getNext().getNext().getItem());

Sample Solution

Note: The debugger breakpoint is on line 5.

Note: The debugger breakpoint is on line 6.

Note: The debugger breakpoint is on line 8.

Output Z

Question 3

Draw the memory map for the following code and write the output given in the final line.

Node n1 = new Node("one");
Node n2 = new Node("two");
Node n3 = new Node("three");

n1.setNext(n2);
n2.setNext(n3);
n1.setNext(n3);

System.out.println(n1.getNext().getItem());

Sample Solution

Note: The debugger breakpoint is on line 5.

Note: The debugger breakpoint is on line 6.

Note: The debugger breakpoint is on line 8.

Note: The debugger breakpoint is on line 9.

Note: The debugger breakpoint is on line 10.

Note: The debugger breakpoint is on line 12.

Output

three

Question 4

Draw the memory map for the following code and write the output given in the final line.

Node n1 = new Node("alpha");
Node n2 = new Node("beta");
Node n3 = new Node("gamma");

n1.setNext(n2);
n2.setNext(n3);

Node p = n1.getNext();
p.setNext(new Node("delta"));

System.out.println(n2.getNext().getItem());

Sample Solution

Note: The debugger breakpoint is on line 5.

Note: The debugger breakpoint is on line 6.

Note: The debugger breakpoint is on line 8.

Note: The debugger breakpoint is on line 9.

Note: The debugger breakpoint is on line 11.

Note: The debugger breakpoint is on line 12.

Note: The debugger breakpoint is on line 14.

Output

delta

Question 5

Draw the memory map for the code below and write the output produced by the following code:

Node n1 = new Node("A");
n1.setNext(n1);
System.out.println(n1.getNext().getNext().getNext().getItem());

Solution

Question 6

Draw the memory map for the code below and write the output produced by the following code:

Node n1 = new Node("A");
n1.setNext(new Node("B", n1));
System.out.println(n1.getNext().getNext().getNext().getItem());
System.out.println(n1.getNext().getNext().getNext().getNext().getItem());

Solution

Question 7

Draw the memory map for the following code and then write the output.

Node player1 = new Node("Mario");
player1.setItem("Luigi");

new Node("Peach", player1);

Node player2 = new Node("Yoshi");
player2.setNext(player1);
player1.setNext(new Node("Bowser"));
player2.getNext().getNext().setNext(new Node("DonkeyKong"));

Node player3 = player2.getNext().getNext();
player3.getNext().setNext(new Node("Toad"));

System.out.println(player3.getNext().getNext().getNext());
System.out.println(player2.getItem());
System.out.println(player1.getNext().getNext().getItem());
System.out.println(player3.getNext().getNext().getItem());

player1.setNext(new Node("Wario"));

System.out.println(player1.getNext().getNext());

Solution

Output

null
Yoshi
DonkeyKong
Toad
null

Note: The debugger breakpoint is on line 4.

Note: The debugger breakpoint is on line 5.

Note: The debugger breakpoint is on line 7.

Note: The debugger breakpoint is on line 9.

Note: The debugger breakpoint is on line 10.

Note: The debugger breakpoint is on line 11.

Note: The debugger breakpoint is on line 12.

Note: The debugger breakpoint is on line 14.

Note: The debugger breakpoint is on line 15.

Note: The debugger breakpoint is on line 22.