Java Programming Lesson-10 | Advanced Scanner Input & Parsing / Reading Strings & Numbers

Java Programming Lesson-10

Welcome to Lesson-10: Advanced Scanner Input & Parsing — this is essential for real-world programs where user input isn’t always simple.

✅ Scanner Class Recap

Scanner is used to take input from the user.

import java.util.Scanner;

Scanner sc = new Scanner(System.in);

Methods:

Method	Reads
nextInt()	Integer
nextFloat()	Float
nextDouble()	Double
next()	Single word String
nextLine()	Full line String

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✅ 1️⃣ Reading Numbers & Strings Together

Problem: Mixing nextInt() and nextLine() can skip input.

Scanner sc = new Scanner(System.in);
System.out.print("Enter age: ");
int age = sc.nextInt();   // reads int

sc.nextLine(); // consume leftover newline

System.out.print("Enter name: ");
String name = sc.nextLine();  // reads full line

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✅ 2️⃣ Parsing Strings to Numbers

Sometimes input comes as String, we need to convert.

String str = "123";
int num = Integer.parseInt(str);       // String → int
double d = Double.parseDouble("12.34"); // String → double

Example:

Scanner sc = new Scanner(System.in);
System.out.print("Enter a number as text: ");
String input = sc.nextLine();
int number = Integer.parseInt(input);
System.out.println("Number + 10 = " + (number + 10));

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✅ 3️⃣ Validating Input Using Try-Catch

Scanner sc = new Scanner(System.in);
System.out.print("Enter an integer: ");
try {
    int num = sc.nextInt();
    System.out.println("You entered: " + num);
} catch(Exception e) {
    System.out.println("Invalid input!");
}

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✅ 4️⃣ Reading Multiple Values in One Line

Scanner sc = new Scanner(System.in);
System.out.println("Enter 3 numbers separated by space:");
int a = sc.nextInt();
int b = sc.nextInt();
int c = sc.nextInt();

System.out.println("Sum = " + (a+b+c));

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✅ 5️⃣ Parsing Complex Input

Example: User enters "25,30,45" → split and parse

Scanner sc = new Scanner(System.in);
System.out.print("Enter numbers separated by comma: ");
String input = sc.nextLine();

String parts[] = input.split(",");
int sum = 0;

for(String p : parts){
    sum += Integer.parseInt(p.trim());
}

System.out.println("Sum = " + sum);

✅ Output (input: 10, 20, 30):

Sum = 60

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📝 Exercise for You ✅

Create a program that:

1️⃣ Takes full name as input
2️⃣ Takes age as input
3️⃣ Takes comma-separated numbers → calculates sum
4️⃣ Handles invalid number input with try-catch

Example Output:

Enter full name: Jitu Hasan
Enter age: 21
Enter numbers separated by comma: 10, 20, 30
Hello Jitu Hasan, Age: 21
Sum of numbers: 60

Reply with:
✅ Your Code
✅ Output

I’ll check & improve it 🔥

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🎯 Quick Quiz

1️⃣ Which Scanner method reads whole line?
A) next()
B) nextLine()
C) nextInt()

2️⃣ Convert "45" (String) to int?
A) Integer.parse("45")
B) Integer.parseInt("45")
C) Integer.toInt("45")

Reply like:
1 → ?, 2 → ?

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✅ Lesson-10 Completed!

✅ NEXT PART - Lesson-11: Object-Oriented Programming (Classes & Objects).