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 de = 1.0;

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

4 / 4 + 6 + de

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 lecperl = true;
double blu = 1.0;
boolean haal = false;

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

lecperl || 8 == blu || haal

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:

• Class relationships: Correct Solution (rguf-o01L-ska2-maxk)
• Static and runtime types: Correct Solution (wt7v-7o8b-k279-d4ch)
• While loops and for loops: Correct Solution (1jj7-8y92-f5rf-ujp)
• Variable scope and lifetime: Correct Solution (geq9-w8ph-ht4i-rwip)