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 hesur = 2;
double chicce = 5.0;
int ge = 7;

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

hesur * 5 - chicce + ge

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 es = 2;

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

5 > 0 || 9 >= es || 0 != 4

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:

• Closures and event handling: Correct Solution (Lwaj-tek8-Ls2c-7io2)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d9h-wnui-99as-2bL2-m)