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:

double hil = 3.0;

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

(hil * 4) - 0

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 su = 5;

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

2 >= 6 && 2 <= su

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

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 (5j9t-wwj4-djs4-rf40)
• Class relationships: Correct Solution (rLq4-8qis-juL9-hfev)
• Variable scope and lifetime: Correct Solution (gf58-agiL-nszb-qu4e)
• Drawing ASTs for expressions: Correct Solution (b4m7-yfnr-q94j-5wd4)