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 amad = 4;
int aenin = 4;

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

1 + amad / (1 - 0 + aenin / 4 / 9 + 7)

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 haph = true;
boolean af = false;
int u = 7;
boolean imiss = true;
double etel = 3.0;
int alpa = 9;
int olmui = 9;
boolean wa = true;

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

haph && af && !(9 < u) || imiss == 1 > etel == alpa >= olmui != wa

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:

• Booleans and conditionals: Correct Solution (5mtm-u26s-i2dL-bk92)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1dah-4z2u-5g3p-x6kn-h)