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 brong = 5.0;
double e = 3.0;
int exlint = 5;
double edoe = 3.0;
int iec = 1;

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

(brong + 9 * e / exlint / edoe) * iec + 7 + 9

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:

boolean cecoen = false;
int rhang = 7;
boolean maon = true;
boolean mixre = false;
boolean feshi = true;

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

(cecoen && 2 > rhang != 1 < 9) == 5 < 1 && maon || mixre != feshi

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 + 7 + "8"

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 (riwv-rj15-73gy-d5aw)
• Class declarations and object modeling: Correct Solution (17ti-7f1n-soes-vs0L-g)