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 chraptmeic = 9;
double scengre = 1.0;

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

chraptmeic + (scengre * 4 / 8 % 1)

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 tet = 9;
double aded = 4.0;
boolean oprun = false;
double ruerchguf = 5.0;
int spioher = 7;

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

(tet == aded || !oprun) && 0 >= 3 || ruerchguf > spioher

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:

• Stack frames and objects (like the Idea Lab activity): Correct Solution (1dak-qmej-4yac-itqd-2)
• Drawing ASTs for expressions: Correct Solution (b2bx-8w57-7ymm-tiht)