Java programming

Statement

A single line of Java code that performs an action

Expression

A combination of variables,values,and operators that produces a result

Assignment Statement

Stores a value in a variable using =

Conditional Statement

Executes code based on a true or false condition

Selection

A control structure that chooses between alternatives

if Statement

Executes code only if a condition is true

if-else Statement

Executes one block if true and another if false

else-if Ladder

Checks multiple conditions in sequence

switch Statement

Selects code to execute based on a variable’s value

Method

A reusable block of code that performs a specific task

Method Definition

The code that specifies what a method does

Method Call

The use of a method to execute its code

Parameter

A value passed into a method

Return Type

The data type a method sends back

void Method

A method that does not return a value

Loop

A structure that repeats code while a condition is met

while Loop

Repeats while a condition is true

do-while Loop

Runs once before checking the condition

for Loop

Repeats using initialization,condition,and update

Infinite Loop

A loop that never stops because the condition is always true

Array

A collection of elements of the same data type

Array Declaration

Defines an array variable

Array Initialization

Assigns values to an array

Array Index

The position of an element starting at 0

Array Length

The number of elements in an array

Traversing an Array

Accessing each element using a loop

Class

A blueprint for creating objects

Object

An instance of a class

Instance Variable

A variable that belongs to an object

Constructor

A special method that initializes objects

this Keyword

Refers to the current object

Inheritance

A mechanism where one class acquires another class’s properties

Superclass

The class being inherited from

Subclass

The class that inherits from another

extends Keyword

Used to inherit a class

Method Overriding

A subclass provides its own version of a method

super Keyword

Refers to the superclass

Encapsulation

Bundling data and methods together and restricting access

Access Modifier

Controls visibility of classes,methods,and variables

public

Accessible from anywhere

private

Accessible only within the class

protected

Accessible within the package or subclasses

Polymorphism

The ability for different objects to respond differently to the same method call

Consider the following Java code fragment.What is the index of the element with value 50?int[] arr={10,20,30,40,50};

4

Consider the following Java code fragment.What will be printed?int[] arr={1,2,3};System.out.println(arr[1]);

2

Consider the following Java code fragment.What happens?int[] arr={5,10,15};System.out.println(arr[3]);

ArrayIndexOutOfBoundsException

Consider the following Java code fragment.How many times does the loop execute?for(int i=0;i<5;i++){System.out.print(i);}

5

Consider the following Java code fragment.What is printed?for(int i=1;i<=3;i++){System.out.print(i);}

123

Consider the following Java code fragment.What is printed?int x=10;if(x>5){System.out.print("Yes");}else{System.out.print("No");}

Yes

Consider the following Java code fragment.What is printed?int x=5;if(x>10){System.out.print("A");}else{System.out.print("B");}

B

Consider the following Java code fragment.What is the final value of x?int x=0;while(x<4){x++;}

4

Consider the following Java code fragment.How many times does the loop execute?int i=0;do{i++;}while(i<3);

3

Consider the following Java code fragment.What is printed?String[] names={"Ann","Bob","Cat"};System.out.println(names[2]);

Cat

Consider the following Java code fragment.What does this code do?for(String s:names){System.out.print(s);}

Prints all elements of the array

Consider the following Java code fragment.What is returned?public static int add(int a,int b){return a+b;}add(2,3);

5

Consider the following Java code fragment.What happens if no return statement exists in a non-void method?

Compile-time error

Consider the following Java code fragment.What is printed?int[] nums=new int[3];System.out.println(nums[0]);

0

Consider the following Java code fragment.What is the array length?int[] arr={7,8,9,10};

4

Consider the following Java code fragment.What keyword is used to inherit a class?

extends

Consider the following Java code fragment.What is the purpose of this constructor?public Car(){}

Initializes a Car object

A while loop always executes at least once

False

Local variables exist only while a method is executing

True

Array indexes in Java start at 1

False

A subclass can override a method from its superclass

True