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 stintbri = 3;
double rarncont = 3.0;
int casphu = 9;
double on = 2.0;
int i = 3;

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

stintbri / 7 % (rarncont % casphu - 5 * on) / i + 9

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:

double e = 5.0;
int mobon = 2;
boolean co = false;
boolean asmtha = false;
int o = 8;
double in = 3.0;
int psurdin = 1;
int wimpas = 5;

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

e >= 0 || 4 > mobon != co || asmtha || 6 != o || !(in >= 6) || psurdin >= wimpas

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?

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