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 qeat = 4.0;
int pangcus = 8;
int ni = 2;

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

8 / (qeat / pangcus + ni)

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 am = 8;
boolean lesmphus = true;

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

am > 2 && (3 < 8 || lesmphus)

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:

• While loops and for loops: Correct Solution (30rb-dvv6-a12z-6ej)
• Class relationships: Correct Solution (rfj8-zqwg-9bkb-3L5v)