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 glu = 5;
int ed = 9;
int iox = 8;

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

glu % ed / 7 - iox % 7 / 5 + 1 + 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 wisma = 9;
boolean bi = true;
boolean swonre = true;
boolean rism = true;
double o = 2.0;
double i = 3.0;

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

8 < wisma && (bi && !(!(3 < 6)) != swonre != rism) && o < i || 3 > 5

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 + 8

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 (17sw-9xe9-Lnsb-irba-9)
• Class relationships: Correct Solution (rj8g-0gfL-j590-a300)