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 estsif = 4;

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

2 * 0 - 5 * estsif

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 dendul = 5;
boolean irfod = true;
boolean pirpchi = true;

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

dendul <= 9 && irfod && pirpchi

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:

• Booleans and conditionals: Correct Solution (5kes-wvyp-vbfh-i034)
• Class relationships: Correct Solution (rj0x-z4y1-vwue-nnur)