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 raqa = 9;
int gesmfra = 7;
int la = 7;
double haun = 4.0;
int pu = 8;

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

raqa * gesmfra * 4 - (la + haun / pu - 4)

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 doua = true;
int i = 4;
boolean mawldeal = true;
int ce = 3;
double piafia = 5.0;
boolean in = false;

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

doua || 8 < i && mawldeal && 2 <= 5 != ce <= piafia && in

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:

• Stack frames and objects (like the Idea Lab activity): Correct Solution (1d8s-fr7z-44r6-swvo-a)
• Closures and event handling: Correct Solution (Lw88-so34-u92c-puLf)
• Drawing ASTs for expressions: Correct Solution (b26v-a8r0-oLjn-zp29)