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 shess = 4.0;
double le = 5.0;

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

5 - shess - 8 / le

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:

double piep = 5.0;
int mak = 3;
boolean tidban = false;
boolean et = false;

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

piep == mak && tidban || et

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 (rfnm-syub-w6vs-f1xm)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d9d-0x6p-zggh-f4w3-g)