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 rosge = 4;
int idpiss = 5;
double soessmoozz = 5.0;

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

0 - 9 / rosge * 6 + idpiss / soessmoozz % 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:

boolean nud = false;
double epaght = 4.0;
boolean onman = true;
boolean howith = false;

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

nud == 7 >= 3 == 8 >= 9 || 3 >= epaght != !onman && howith

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:

• Booleans and conditionals: Correct Solution (5nco-vado-yhhu-3fog)
• Closures and event handling: Correct Solution (Lw65-hyie-419v-imcd)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d8y-ytgf-kped-1ktd-r)