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 glefi = 3;
double dintfa = 5.0;

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

1 + glefi - (dintfa - 3)

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 assphel = false;
boolean e = true;
int cencas = 9;

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

assphel && (e || 6 <= cencas)

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"

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:

• Static and runtime types: Correct Solution (wtb8-h2oy-0w0r-vcLf)
• Drawing ASTs for expressions: Correct Solution (b40y-fjx5-y7tm-5db9)
• Class declarations and object modeling: Correct Solution (17um-t9n9-rbnn-d9cx-a)