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:

int celnoin = 3;
int esstur = 6;
int redfal = 3;
double ti = 5.0;

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

celnoin % 8 - (9 / esstur) + redfal - ti

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 qultec = 2;
int je = 3;
boolean id = true;
boolean edpad = false;

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

qultec == 7 && je < 4 && id != edpad && !(4 >= 9)

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 + 6

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:

• Class relationships: Correct Solution (rkgd-ocmc-xscq-6a2d)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d8s-5bvy-rnaw-o6Lb-k)