Operators and Decision Constructs

Question 1

Which types can be used as switch variables?

Answer 1

String, byte, char, short, int, and enum, as well as their respective wrapper classes.

Question 2

T/F: Case constants must be assignable to the switch variable.

Answer 2

True.

Question 3

T/F: If the switch variable is of the String type, you can still use int for the case labels

Answer 3

False.

Question 4

Will this compile:

byte b = 10;

switch(b) {
case 300: //valid code;
}

Answer 4

No.

The case constants cannot be bigger than what the switch variable can store.

Question 5

Can there be more than one case constant with the same value in a switch statement?

Answer 5

No.

Question 6

T/F: There can be multiple labels for a a switch statement.

Answer 6

False.

Question 7

Which operators will not necessarily evaluate all operands?

Answer 7

||
? :
&&

Question 8

What are the integral types?

Answer 8

byte, short, int, long, and char.

These are primitive types which can holder integer values.

Question 9

T/F: The modulus operator can only be used on integer operands.

Answer 9

False.

It can also be used on floating point operands.

Question 10

Is this statement legal:

if (false) ; else ;

Answer 10

Yes.

An if-clause and else-clause can have empty statements.

Question 11

T/F: An abstract class can be extended by an abstract class or a concrete class

Answer 11

True

Question 12

T/F: A concrete class can be extended by an abstract or concrete class.

Answer 12

True

Question 13

T/F: An Interface can be extended by another interface

Answer 13

True

Question 14

T/F: An interface can be extended by an abstract class.

Answer 14

False.

A class implements an interface, not extend.

Question 15

T/F: An interface can be extended by a concrete class.

Answer 15

False.

Question 16

T/F: An abstract class cannot implement an interface.

Answer 16

False.

Any class can implement an interface.

Question 17

What is the order of access modifiers from most restrictive to least?

Answer 17

private > default (no modifier) > protected > public

Question 18

From where are private members accessible?

Answer 18

Only from within the class itself.

Question 19

From where can a member with default access (no modifier) be accessed?

Answer 19

From within the class itself or classes in the same package.

Question 20

From where can a protected member be accessed?

Answer 20

From within the class itself or from within the same package.

Question 21

From where can a public member be accessed?

Answer 21

From anywhere.

Question 22

What is at the root of any inheritance hierarchy?

Answer 22

Object

Question 23

Which operator takes precedence ` != ` or ` = ` ?

Answer 23

The boolean operator ` != ` takes precedence over the assignment operator ` = `

Question 24

Which operator takes precedence, the dot operator or the cast operator?

Answer 24

The dot operator takes precedence over the cast operator.

A dot operator (or separator):
objectReference.methodName(argumentList);

A cast operator:
(Integer)

Question 25

What is the result of the following code?

boolean b1 = false;
boolean b2  = false;
if (b2 = b1 == false){
   System.out.println("true");
} else{
   System.out.println("false");
}

Answer 25

It prints true.

Remember that every expression has a return value.