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 shielic = 2.0;
double eocas = 3.0;

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

(shielic / 4 * 7) - eocas

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 pnelpo = 5.0;
double ad = 4.0;
int ba = 5;

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

(pnelpo != 8 || ad > ba || 2 != 3)

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 relationships: Correct Solution (rfi1-q1a8-4vec-7vpL)
• Variable scope and lifetime: Correct Solution (gf5h-Luis-hqkn-vty5)