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 siucdes = 2;

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

siucdes * 1 * 6 + 8 % 8

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 o = true;
int oinct = 7;
int e = 9;
double tecus = 3.0;
boolean ochil = true;

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

o && 9 == oinct || (e >= tecus || ochil)

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)

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:

• Drawing ASTs for expressions: Correct Solution (b4n4-b5do-o160-2v28)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d85-0tkr-cn0c-zo2n-d)