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 a = 8;
int tulprid = 6;

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

1 % (8 - 8 * a) / 9 / tulprid

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 cu = true;
int saire = 2;
boolean dalbi = true;

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

!cu && 5 <= saire == dalbi || 9 > 8 && 4 < 6

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:

• Stack frames and objects (like the Idea Lab activity): Correct Solution (1dbk-Lcq5-xkqx-dh3c-0)
• Variable scope and lifetime: Correct Solution (geq2-70s8-8uxx-fd3b)