Drawing ASTs for expressions: Correct Solution

For each of the Java expressions below:

• Draw an AST for the expression.
• Show how the expression evaluates at each node in the tree.

Be sure that your tree accurately reflects how Java would evaluate the expression.

Part 1

Given the following variables:

double ormi = 1.0;
int bormchol = 6;
int re = 3;

...draw the AST and evaluation results for the following expression:

ormi + 3 / bormchol * 7 % re

Solution

Things to double-check in your solution:

• Do you have the left and right branches on the correct side?
• Did you indicate the difference between ints and floating point values?

Part 2

Given the following variables:

int ucia = 5;
double de = 5.0;
boolean braacs = true;
boolean chae = true;

...draw the AST and evaluation results for the following expression:

ucia <= de || 9 <= 8 && braacs || !chae

Solution

Things to double-check in your solution:

• Does your tree correctly reflect the precedence of && and ||?
• Did you correctly show short-circuiting? (That is when the right branch of && or || is never evaluated because the left branch already determines the answer.)

Part 3

Draw the AST and evaluation results for the following expression:

(0 + 1 + 2) + 3 + 4 + "5"

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

Related puzzles:

• Closures and event handling: Correct Solution (Lwi5-3qvn-05cr-7c7p)
• Static and runtime types: Correct Solution (wtpa-gtzs-qyqn-wc5e)