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 medspusm = 5;

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

0 * 6 - medspusm

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:

double tietro = 5.0;
double pesmnin = 3.0;
int wi = 1;
int er = 9;

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

tietro > pesmnin || wi < er

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

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:

• Static and runtime types: Correct Solution (wtrp-y2zv-uxpp-mkgq)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d9r-vpw8-giez-b32b-p)
• Drawing ASTs for expressions: Correct Solution (b20c-r0ef-3xcL-369n)