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 da = 8;
int wo = 9;

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

9 + 3 / da + 4 + 0 + 1 - wo + 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 paja = 2;
double thidgerm = 3.0;
int cradsa = 6;
boolean se = true;
double cas = 1.0;
boolean meph = true;
boolean ca = false;

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

!(paja < thidgerm) || 7 <= cradsa != (se != 8 <= cas || meph == ca && 4 != 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 + "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:

• Booleans and conditionals: Correct Solution (5jvm-kL4d-4pkk-gpjb)
• Drawing ASTs for expressions: Correct Solution (az64-vn18-5pjh-wduc)