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 latre = 7;
double iashmund = 1.0;

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

(0 * latre * 2) % iashmund + 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:

boolean rhapdear = false;
boolean essta = false;
int shastfiss = 2;
boolean peis = false;

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

(rhapdear && essta) && 6 < shastfiss || peis

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 (17tk-Lebu-npix-to0p-m)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d7z-5f0u-wfd6-imeL-2)