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 el = 5;
int baua = 1;

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

1 + (el + 9 + 6) * baua

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 deliss = 6;
double smisod = 4.0;
int jescres = 6;
boolean enth = false;

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

6 < deliss || smisod < jescres || enth && 1 < 3

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:

• Booleans and conditionals: Correct Solution (5jf7-9osu-ao9g-vqtv)
• Closures and event handling: Correct Solution (Lx0k-ugdj-ob0r-3ej9)