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 uchaeond = 5;
double aness = 1.0;

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

5 * 6 % uchaeond + aness * 5 + 4

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 ur = 3;
boolean hanian = false;
int a = 7;
boolean o = false;
boolean du = true;

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

ur != 8 != hanian && a == 3 || (!o == du)

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

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 (5Lm4-65ai-xdv0-mj7d)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1day-6kx5-h53o-g6xx-j)
• Variable scope and lifetime: Correct Solution (gers-wymw-gki4-xj6b)
• While loops and for loops: Correct Solution (324s-g74y-yu24-ukj)