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 idhomp = 8;
double ce = 3.0;

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

0 % idhomp % 4 * ce * 7

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 gliargiou = 4;
int iger = 7;
boolean frargel = true;

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

4 > gliargiou || 0 == 7 && iger < 2 && frargel

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:

• Class declarations and object modeling: Correct Solution (17t7-p6b1-vz4t-swuf-z)
• Drawing ASTs for expressions: Correct Solution (b525-6kpe-quph-pest)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d8j-hxg6-3uqq-1w4p-7)