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 idcec = 2.0;
int hism = 4;
double ghun = 2.0;

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

5 + 7 + idcec + hism * ghun

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 cresstre = true;
int deplad = 7;
double cordoss = 5.0;
double hoimil = 1.0;
int i = 7;
double rostfir = 4.0;

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

cresstre || 8 <= deplad || !(cordoss == hoimil) || i < rostfir

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

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 (17xa-s8b7-vbm8-chbp-r)
• Variable scope and lifetime: Correct Solution (gf62-euu9-7dte-jn0v)