Misc

Question 1

what are 4 fundamental data types in java

Answer 1

int, float, character, boolean;

Question 2

size and range of byte in java

Answer 2

1 byte and +127 to -128

Question 3

size and range of short in java

Answer 3

2 byte and +32767 to -32768

Question 4

size and range of int in java

Answer 4

4 byte and +x to -(x+1)

Question 5

size and range of long in java

Answer 5

8 byte and +y to -(y+1)

Question 6

size of float in java

Answer 6

4 bytes

Question 7

size of double in java

Answer 7

8 bytes

Question 8

The letter ‘f’ must follow these type of constants

Answer 8

float type(float and double)

Question 9

default initial value of int

Answer 9

zero(0)

Question 10

default initial value of float

Answer 10

zero(0.0)

Question 11

default initial value of character

Answer 11

NA

Question 12

default initial value of boolean

Answer 12

false

Question 13

Two types of programming languages are:

___ oriented and ___ oriented

Answer 13

Procedural and Object

Question 14

Difference between class and objects

Answer 14

Class exists logically; it has no space allocated in memory to it; is loaded only once in memory while execution; resides in disk as 
object is allocated space when it is created; based on its parent class definition; reside in main memory

Question 15

Data members of a class are also known as

Answer 15

properties/fields/attributes

Question 16

methods of a class are also known as

Answer 16

behaviors/accessories

Question 17

File name should be the same as the ___ name

Answer 17

Class name; although this is convention and not a rule

Question 18

Command to execute a java program

Answer 18

java ClassName; make sure that ClassName.class exists so that ClassLoader can put it into main memory.

Question 19

4 ways to input data to Java program

Answer 19

Keyboard; command prompt; file reading; xml file

Question 20

Autoboxing/Unboxing is done by ____

Answer 20

Java Compiler

Question 21

What are default packages and they are imported by whom?

Answer 21

packages that need not be explicitly imported in java programs;
put internally by java compiler

Question 22

System class belongs to this package

Answer 22

java.lang

Question 23

Use of this keyword

Answer 23

differentiate between members of class and formal parameters of same name.

Question 24

obj1.method_name(obj2);

obj1 and obj2 are

Answer 24

source/invoking object, and destination/target object respectively.

Question 25

5 types of inheritance are

Answer 25

single/multilevel/multiple/hierarchical/hybrid

Question 26

If we don't want our class to be inherited, we must define it as ___ class

Answer 26

final class

Question 27

If we don't want to give some methods/members of base class to derived class

Answer 27

the must be declared private

Question 28

Java does not allow ___ classes however ___ ___ classes are allowed

Answer 28

private, and Inner Private

Question 29

scope of base class object is ___

Answer 29

can access base class objects but not derived class objects.

Question 30

types of relationships between classes in java

Answer 30

is_a, has_a, and uses_a

Question 31

is_a relationship uses ___ keyword

Answer 31

extends

Question 32

is_a relationship follows ___ memory management

Answer 32

logical

Question 33

define has_a relationship

Answer 33

an object of one class is used as data member of another class

Question 34

define uses_a relationship

Answer 34

a method in the class uses an object of another class.

Question 35

All java classes have a default ___ relationship because ___ class is base of all classes

Answer 35

is_a, Java.Lang.Object

Question 36

example of has_a relationship

Answer 36

System.out which contains out, out is an object of the PrintStream class.

Question 37

super keyword is used for

Answer 37

accessing same name methods/members of the base class in the derived class.

Question 38

When derived class constructor is called the constructors of base class are called ____ but are executed ___

Answer 38

bottom-to-top; top-to-bottom

Question 39

use of this() constructor

Answer 39

calls current class default constructor from current class parameterized constructor

Question 40

use of this(....) constructor

Answer 40

used to call current class constructor from other constructors

Question 41

when using this() and this(....) we must avoid having ___

Answer 41

cyclic calling of constructors.

Question 42

two ways to implement polymorphism with methods in java

Answer 42

method overloading; method overriding

Question 43

two types/principles of polymorphism

Answer 43

static/compile time polymorphism; | dynamic/run time polymorphism

Question 44

we can't create an object of an abstract class directly, but we can do so by ___

Answer 44

creating an implementation/derived class.

Question 45

abstract method cannot be ___, ___ & ___

Answer 45

private, final, static

Question 46

what are the two types of packages in java

Answer 46

1) pre-defined/built-in 2) user-defined

Question 47

This package is also called the default package in java

Answer 47

java.lang.*; it is imported by default in all classes.

Question 48

java.lang.* has these following five basic facilities

Answer 48

1) command line arguments 2) data conversions 3) garbage collection 4) developing thread based apps 5) developing exception based apps

Question 49

private modifier is also known as ___

Answer 49

native access modifier

Question 50

default modifier is also known as ___

Answer 50

package access modifier

Question 51

protected access modifier is also known as ___

Answer 51

inherited access modifier

Question 52

public access modifier is also known as ___

Answer 52

universal access modifier

Question 53

is default a keyword in java?

Answer 53

no

Question 54

what are the three types of errors we get in all programming languages?

Answer 54

1) compile time errors 2) logical errors 3) run time errors

Question 55

what is a logical error?

Answer 55

logical errors are errors that produce wrong result according to business logic,

Question 56

how is a logical error different from a runtime error?

Answer 56

runtime errors don't produce any wrong output, they simply terminate the program. they are a result of invalid operation/input.

Question 57

what are the two types of exceptions?

Answer 57

1) pre-defined/built-in exceptions | 2) user/programmer/custom-defined exceptions

Question 58

pre-defined exceptions are of two types. what are they?

Answer 58

synchronous and asynchronous types

Question 59

synchronous exceptions are of two types. what are they?

Answer 59

checked and un-checked

Question 60

5 keywords often used when handling exceptions

Answer 60

1. try 2. catch 3. finally 4. throw 5. throws

Question 61

nested try blocks are permitted in java. true/false

Answer 61

true

Question 62

one can write try catch blocks in finally. true/false

Answer 62

true

Question 63

out and err are objects of which class?

Answer 63

PrintStreamClass, which are used in System class

Question 64

3 ways to print error messages in exceptions

Answer 64

1. print object of Exception/Throwable class. 2. use printStackTrace() 3. use getMessage() in Exception object

Question 65

2 ways of creating a thread class

Answer 65

using: 1. java.lang.Thread class 2. java.lang.Runnable interface

Question 66

use, and prototype of setName, and getName in Thread class

Answer 66

used to set user-friendly names for threads public final void setName(String); public final String getName();

Question 67

use, and prototype of setPriority, and getPriority in Thread class

Answer 67

public final void setPriority(int); | public final int getPriority();

Question 68

use, and prototype of isAlive()

Answer 68

true if thread is in execution; false otherwise(halted state, or new state) public boolean isAlive()

Question 69

use of public void run()

Answer 69

in this method we write the java code that has to be executed by the thread. it is a null body method that we override from the Thread class.

Question 70

use of public final void start()

Answer 70

1. moves thread from READY to NEW state 2. provides multithreading services(concurrency, synchronization, and ITC) 3. automatically calls run() which contains the logic of thread

Question 71

use of suspend()

Answer 71

puts a thread into WAITING state. suspends its execution. it can be resumed from here.

Question 72

use of resume()

Answer 72

move a thread from WAITING state to READY state | thread continues execution from where it had started.

Question 73

use of stop()

Answer 73

move a thread into the HALTED state | thread stops execution completely, and cannot be resumed from there.

Question 74

use of public final ThreadGroup getThreadGroup()

Answer 74

get the thread group name of foreground thread

Question 75

use of 'public static final Thread currentThread()'

Answer 75

it is a factory method | returns all the thread that are currently running

Question 76

use of 'public static final void sleep(long)'

Answer 76

makes a thread pause for certain number of milliseconds

Question 77

ThreadGroupName always resides in this method

Answer 77

main()