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What is the purpose of the Scanner class in Java?
What is the purpose of the Scanner class in Java?
The Scanner class in Java is used to obtain input from the user or a file. It allows the program to read data from various input sources such as the keyboard, console, files, or strings.
What is the purpose of a constructor in Java?
What is the purpose of a constructor in Java?
Constructors are special methods in Java that initialize objects. They are responsible for setting the initial state of an object when it is created.
Is the Scanner class used to read data from a file in java?
Is the Scanner class used to read data from a file in java?
True
Which of the following is a valid way to create an object of the Student class?
Which of the following is a valid way to create an object of the Student class?
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What does the print() function in java actually do?
What does the print() function in java actually do?
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What does the println() function do in Java?
What does the println() function do in Java?
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Which built-in Java class is commonly used to read input from the user?
Which built-in Java class is commonly used to read input from the user?
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What is the role of access modifiers in Java?
What is the role of access modifiers in Java?
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Study Notes
Programming Languages in Java
- Java is an object-oriented programming language.
- Object-oriented programming (OOP) is based on the concept of objects having properties and behaviors.
- Objects interact with each other using methods (functions).
Java Classes and Objects
- A class is a blueprint for an object.
- An object is an instance of a class.
- Classes define properties (variables) and methods (functions).
Java Access Modifiers
- Public: Accessible from anywhere.
- Protected: Accessible within the same package and by subclasses.
- Default (Package-Private): Accessible within the same package only.
- Private: Accessible only within the same class.
Control Structures
-
if-else: Conditional statements.
- if(condition) { statement1; } // Execute statement1 if the condition is true
- else { statement2; } // Execute statement2 if the condition is false
-
if-else if-else: Multiple conditions
- if(condition1) { //Execute st1 if cond1 is true
- else if(condition2) { // Execute st2 if cond2 is true
- else { // Execute else part if none of the conditions are true. }
- switch: A choice structure used to select among multiple blocks of code.
switch (expression) {
case value1: // execute if expression matches the value 1
statement1;
break;
case value2: //execute if expression matches value2
statement2;
break;
default: //execute if expression matches none of the values
defaultStatement;
break;
}
-
for loop: Repeated execution of a block of code.
-
for(initialization; condition; increment/decrement){ //block of statements}
-
-
while loop: Repeated code execution as long as a condition is true.
-
while(condition){ //statements }
-
-
do-while loop: Repeated code block at least once then repeats as long as a condition is true.
-
do { //statements } while (condition);
-
Java Scanner
- The
Scannerclass is used to read input from various sources.-
Scanner scanner = new Scanner(System.in);creates a Scanner object to read from the keyboard,scanner = new Scanner(file);to read from a file,scanner = new Scanner(str);to read from a string .
-
- Use methods
next(),nextInt(),nextDouble(),nextLine(). for different data types.
Java Constructors
- Constructors are special methods that are invoked when an object of a class is created.
- They have the same name as the class.
- They initialize object variables.
Example Code (from the documents)
import java.util.Scanner;
public class Test {
public static void main(String[] args) {
String s = "Hello World! 3 + 3.0 = 6";
Scanner scanner = new Scanner(s);
System.out.println(scanner.nextLine()); // Prints the entire line
}}
import java.util.Scanner;
public class Test {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("enter the first Num ");
int x = scanner.nextInt();
System.out.print("enter the second Num ");
int y = scanner.nextInt();
int z = x + y;
System.out.println("the result is " + z);
}}
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Description
This quiz covers essential concepts in Java programming, including object-oriented programming, classes and objects, access modifiers, and control structures. Test your understanding of how these elements work together to create robust Java applications.
