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 venbros = 5.0;
double nempre = 4.0;
int on = 6;

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

venbros % nempre + (0 * on)

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 glun = 4;
int ce = 2;
boolean afca = false;
double icpnol = 3.0;
int getong = 3;

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

glun == ce && afca || icpnol < getong

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

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:

• Drawing ASTs for expressions: Correct Solution (b3zk-9zxb-vmio-b6k1)
• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d9q-pdqo-yq7g-4mkL-7)
• Static and runtime types: Correct Solution (wt8a-2geb-tdox-f8p6)