Java Basics

Question 1

Where is a local variable defined?

Answer 1

In a method.

Question 2

Where are instance members defined?

Answer 2

In the scope

Question 3

T/F: An instance member can be a variable, constant or method

Answer 3

True

Question 4

What is an instance member?

Answer 4

A member variable or method that belongs to a specific object instance.

Question 5

T/F: Non-static members are instance members.

Answer 5

True

Question 6

Does Java support multiple package statements?

Answer 6

No

Question 7

Where does the package statement go in a file?

Answer 7

The first statement in the file.

Question 8

What happens if no argument is passed to a main method?

Answer 8

The args parameter is then an array of Strings of length zero.

Question 9

How do you declare a method where an instance of the class is not needed?

Answer 9

Use the static keyword.

Question 10

What is the correct parameter specification for the standard main method?

Answer 10

(String[ ] args)

or

(String args [ ] )

Question 11

What does “class-level” mean in terms of access?

Answer 11

It means being accessible from anywhere (i.e. static as well as non-static methods) in the class (and from outside the class depending on their access modifier). This is done by using static methods.

Question 12

What does “instance level” mean in terms of access?

Answer 12

It means accessible only from instance methods in the class. This is done with instance fields.

Question 13

Which classes have access to a member with no modifier (default)?

Answer 13

Only members within the same package.

Question 14

What is the visibility of local variables?

Answer 14

They are always accessible within the block in which they are declared.

Question 15

Which modifiers can be applied to local variables?

Answer 15

Only final.

They cannot be transient, volatile, static, public or private.

Question 16

Transient

Answer 16

An access modifier which marks the member variable as not to be serialized when persisted to streams of bytes.

Question 17

Volatile

Answer 17

Access modifier which lets the JVM know that a thread accessing the variable must always merge its own private copy of the variable with the master copy in memory.

Question 18

Native

Answer 18

Access modifier applied to a method to indicate that the method is implemented in native code using JNI (Java Native Interface).

Cannot be applied to any kind of variable. (Methods only.)

Question 19

Synchronized

Answer 19

Access modifier applied to blocks on some object and can only have one thread executing inside them at a time

Question 20

What must be the return value of the main() method?

Answer 20

Void

Question 21

What commands must be run to compile and have the following code print “hello”:

public class Foo{
  public static void main(String[] args){
     System.out.println(args[1]);
  }
}

Answer 21

javac Foo.java

java Foo hello hello

Question 22

Consider:

package.com.foo.*

Is this a valid package statement?

Answer 22

No.

A package can never have a wildcard *.

Question 23

Which is the only package imported automatically?

Answer 23

java.lang

Question 24

What must be imported if the code uses IOException?

Answer 24

The java.io package (or just the java.io.IOException class)