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 qi = 7;
double gecead = 3.0;

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

4 % qi - 6 + 4 % gecead % 5

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 e = false;
boolean nontnoun = true;
int voo = 4;
int ioa = 2;

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

e || 6 <= 1 != nontnoun || voo >= 1 == !(2 <= ioa)

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:

• Variable scope and lifetime: Correct Solution (gf06-jgnc-njto-zguh)
• Class declarations and object modeling: Correct Solution (17vw-jjb4-en9i-z3ta-e)