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 erla = 1;
int thesoilch = 7;
int i = 7;
int riock = 2;
double aglo = 3.0;
int plequl = 3;

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

erla % thesoilch - i - riock % 6 % aglo % (2 % plequl)

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 de = 1.0;
double edmuc = 3.0;
int un = 6;
int mafnic = 9;
int oa = 5;
double kihess = 4.0;
boolean zaph = true;

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

de > 5 || edmuc != 3 != (3 != un) == mafnic <= oa != 6 <= 2 && kihess >= 4 != zaph

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 + 8

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 (rjsk-4p1d-36md-zLtu)
• Class declarations and object modeling: Correct Solution (17vn-jkp2-au43-ewfn-4)