Program 3 : String Class and Scanner

Explore the String class and command-line arguments by developing a program that manipulates strings and processes arguments. Additionally, demonstrate the use of varargs and the Scanner class for input.

import java.util.Scanner;

public class SimpleStringExplorer {

    public static void main(String[] args) {
        if (args.length == 0) {
            System.out.println("Usage: java SimpleStringExplorer <some-text>");
            return;
        }
        
        String initialText = args[0];
        System.out.println("Argument received: \"" 
            + initialText + "\"");


		System.out.println("\n## String Manipulation ##");
        manipulateString(initialText);


		System.out.println("\n## Varargs Demonstration ##");
        String sentence = joinStrings(" ", "Varargs", "is", "simple.");
        System.out.println("Joined sentence: " + sentence);


		System.out.println("\n## Scanner Demonstration ##");
        Scanner scanner = new Scanner(System.in);
        System.out.print("Please enter your name: ");
        String name = scanner.nextLine();
        System.out.println("Hello, " + name + "!");
        
        scanner.close();
    }


    public static void manipulateString(String text) {
        System.out.println("Length: " + text.length());
        System.out.println("Uppercase: " + text.toUpperCase());
        System.out.println("Lowercase: " + text.toLowerCase());

        // Get the character at a specific index
        if (!text.isEmpty()) {
            System.out.println("Character at index 0: " 
	            + text.charAt(0));
        }

        // Check if the string starts with a certain prefix
        System.out.println("Starts with 'Hello': " 
	        + text.startsWith("Hello"));

        // Find the index of a character or substring
        System.out.println("Index of 'J': " 
	        + text.indexOf('J'));

        // Replace all occurrences of a character
        System.out.println("Replacing 'a' with '@': " 
	        + text.replace('a', '@'));
        
        // Get a portion of the string
        if (text.length() > 5) {
            System.out.println("Substring from index 5: " 
	            + text.substring(5));
        }
        
        // Demonstrate trimming whitespace from the beginning and end
        String paddedText = "   some spaces   ";
        System.out.println("Trimming '" 
	        + paddedText + "': '" + paddedText.trim() + "'");
    }


    public static String joinStrings(String separator, String... words) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < words.length; i++) {
            sb.append(words[i]);
            // Add the separator unless it's the last word
            if (i < words.length - 1) {
                sb.append(separator);
            }
        }
        return sb.toString();
    }
}

---

java SimpleStringExplorer "HelloJava"

Argument received: "HelloJava"

## String Manipulation ##
Length: 9
Uppercase: HELLOJAVA
Lowercase: hellojava
Character at index 0: H
Starts with 'Hello': true
Index of 'J': 5
Replacing 'a' with '@': HelloJ@v@
Substring from index 5: Java
Trimming '   some spaces   ': 'some spaces'

## Varargs Demonstration ##
Joined sentence: Varargs is simple.

## Scanner Demonstration ##
Please enter your name: Alex
Hello, Alex!

Mess of a Program

import java.util.Scanner;

class Box {
    double width, height, depth;

    Box(double w, double h, double d) {
        width = w;
        height = h;
        depth = d;
    }

    public String toString() {
        return "The dimensions are " + width 
	        + " by " + height + " by " + depth + ".";
    }
}

public class ToStringDemo {

    // Method using varargs
    static void printWords(String... words) {
        System.out.println("Words passed using varargs:");
        for (String word : words) {
            System.out.println(word);
        }
    }

    public static void main(String[] args) {
        // Box and toString
        Box b = new Box(10, 12, 14);
        String s = "The box b is " + b;
        System.out.println("Printing b: " + b); // Converted to string using toString
        System.out.println("Printing s: " + s);

        // String manipulation
        String s2 = "Face the failure until the failure fails to face you";
        int start = 4;
        int end = 37;
        char[] buf = new char[end - start];
        s2.getChars(start, end, buf, 0);

        System.out.println("Extracted substring using getChars:");
        System.out.println(buf);

        // Command-line arguments
        System.out.println("The number of command-line arguments: "
	         + args.length);
        for (int i = 0; i < args.length; i++) {
            System.out.println("Argument " 
	            + (i + 1) + ": " + args[i]);
        }

        // Varargs method
        printWords("Java", "String", "Scanner", "Varargs");

        // Scanner input
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter a sentence: ");
        String input = sc.nextLine();
        System.out.println("You entered: " + input);
        sc.close();
    }
}

Case 1: No Command-line Arguments

Printing b: The dimensions are 10.0 by 12.0 by 14.0.
Printing s: The box b is The dimensions are 10.0 by 12.0 by 14.0.
Extracted substring using getChars:
the failure until the failure fa
The number of command-line arguments: 0
Words passed using varargs:
Java
String
Scanner
Varargs
Enter a sentence: change is constant
You entered: change is constant

Case 2: With Command-line Arguments

F:\MSRIT\JAVA\Lab>java ToStringDemo Hello world
Printing b: The dimensions are 10.0 by 12.0 by 14.0.
Printing s: The box b is The dimensions are 10.0 by 12.0 by 14.0.
Extracted substring using getChars:
the failure until the failure fa
The number of command-line arguments: 2
Argument 1: Hello
Argument 2: world
Words passed using varargs:
Java
String
Scanner
Varargs
Enter a sentence: this is java lab
You entered: this is java lab