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 udphent = 4;
int sossin = 1;

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

udphent * 1 * 9 - sossin + 0 / 7 + 8

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 flodar = 8;
int phusmess = 4;
int a = 7;
boolean u = false;
double peodco = 3.0;
double qulsen = 1.0;

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

8 >= flodar || phusmess == a != (5 == 3) == !(7 > 4) && (u && peodco >= qulsen)

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 + 7

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 declarations and object modeling: Correct Solution (17sy-6kb0-vw8j-1xqv-5)
• Variable scope and lifetime: Correct Solution (geyb-qvnj-nxe9-7Le6)