Chapter 2

Question 1

Order of operators?

Answer 1

Post unary: x++, x--
Pre unary: ++x, --x
Other unary: +,-,!
Multiplication etc: *,/,%
Addition etc: +,-
Shift operators: <>,>>>
Relational operators: ,<=,instanceof
Equal to etc: ==, !=
Logical operators: &amp;,^,|
Short circuit: &amp;&amp;, ||
Ternary: boolean?exp1:exp2
Assignment ops: =,+=,*= etc

Question 2

4 numeric promotion rules:

Answer 2

Java promotes to larger of the data types.
Integral promoted to floating point.
Byte, short and char promoted to Int first, even if none are Int.
The result has same data type as promoted operands.

Question 3

What is data type of x * y / z?
short x = 14;
Float y = 13;
Double z = 30;

Answer 3

X promoted to Int, then to float. Result of x*y promoted to double. Result is a double.

Question 4

–x means?

Answer 4

Operator applied first, value return is the new value.

Question 5

X–

Answer 5

Original value is returned, then the operator is applied.

Question 6

Int x = 3;
Int y = ++x * 5 / x– + –x;
X?
Y?

Answer 6

X is 2

Y is 7

Question 7

short z = x * y;

Doesn’t compile, why?

Answer 7

Because short values are automatically promoted to Int when applying arithmetic operator. And short variable cannot be set to Int value.

Question 8

Which works?
long x = 10;
int y = 5;
A) y *= x;
B) y = y * x;

Answer 8

A works. B does not compile.

Question 9

Is this valid:

long x = (x = 3);

Answer 9

Yes

Question 10

X ^ Y = ?

1) t t
2) t f
3) f t
4) f f

Answer 10

1) false
2) true
3) true
4) false

Question 11

Difference between & an &&?

Answer 11

&& short circuits and right hand side of a statement may never be evaluated.

Question 12

Why does this not through exception:
Integer x;
If(x != null && x.getValue() < 5) {}

Answer 12

Because && short circuit prevents x.getValue() from ever being reached.

Question 13

File x = new File("s.txt");
File y = new File("s.txt");
File z = x;
A) x == y ?
B) x == z ?

Answer 13

Checks references point to same object, not for object equivalence. So…
A) false
B) true

Question 14

Write the following as if else’s:
Int y = 10;
Int x = (y > 5) ? (2 * y) : (3 * y);

Answer 14

Int y = 10;
Final Int x;
If (y > 5) {
 X = 2 * y;
} else {
 X = 3 * t;
}

Question 15

What target types can a switch statement have?

Seitch(targetType) {}

Answer 15

int and all primitives that can be promoted to int (byte, short, char). Also enum. Also Byte, Short, Charachter, Integer. Also String.

Question 16

Is this legal?

for(;;){ }

Answer 16

Yep

Question 17

Is this legal?

for(long y=0, z=4;x<5 && y<10; x++, y++) { }

Answer 17

Yep