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 ingoud = 5;
double fach = 2.0;

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

9 * 6 - 9 / ingoud * fach

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 ushi = true;
double pedda = 5.0;

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

7 >= 8 || (1 == 3 && ushi || 1 == pedda)

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 (17xa-ozyr-isqj-6juL-t)
• Class relationships: Correct Solution (rg7a-q4yp-3qp3-gkvn)