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 feac = 4;
double pinoss = 5.0;
int a = 9;

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

(feac % 5 - pinoss) % a

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 pi = 6;
int bamle = 4;
boolean bir = false;

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

pi >= bamle || 3 <= 3 || bir

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

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 (17wy-cqzk-fc62-3osr-i)
• Closures and event handling: Correct Solution (Lzve-qcm1-s617-dxm0)
• Static and runtime types: Correct Solution (wtr9-gh7c-kggi-xszh)