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 todiod = 3.0;
int niwrurch = 3;

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

9 * 7 - todiod * 2 + 3 + niwrurch * 5

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 tu = 7;
int el = 2;
int grih = 1;
int ol = 3;

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

4 > tu && 7 >= 9 && (1 == el == (grih != 6) && 1 >= 0) != ol > 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 + 5 + "6" + "7"

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:

• Variable scope and lifetime: Correct Solution (gf1h-w97k-dufk-m0td)
• Class relationships: Correct Solution (riav-i54v-egks-Lrkm)
• Booleans and conditionals: Correct Solution (5paw-1y95-wxqq-397x)