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 hislul = 4.0;
int sphosscross = 5;
int enfle = 2;
int thre = 4;

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

hislul - (sphosscross + 3 + 1 + 7 * enfle + thre)

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 berd = 1;
int ento = 7;
boolean be = true;
boolean edpec = true;
boolean siunt = false;
double ta = 3.0;

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

berd == 4 && ento >= 9 == be != edpec != siunt || ta == 0

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:

• While loops and for loops: Correct Solution (2yxe-hw1c-osbv-pom)
• Class relationships: Correct Solution (rgLt-3p5d-fr3n-gu1d)