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HTML / CSS / JS

public class StringsAndScope {

// Class-level constant (static final)
    private static final int MAX_ITEMS = 100;

// Instance variable
    private String label;

public StringsAndScope(String label) {
        this.label = label;  // 'this' disambiguates instance vs parameter
    }

public void demonstrateStrings() {
        // String immutability
        String s = "hello";
        s.toUpperCase();         // returns new String, does NOT modify s
        System.out.println(s);   // still "hello"

String upper = s.toUpperCase(); // must capture return value
        System.out.println(upper);      // "HELLO"

// Common String methods
        String text = "  Java Programming  ";
        System.out.println(text.trim());           // "Java Programming"
        System.out.println(text.trim().length());  // 16
        System.out.println(text.contains("Java")); // true
        System.out.println(String.join(", ", "a", "b", "c")); // "a, b, c"

// StringBuilder for efficient concatenation
        StringBuilder sb = new StringBuilder();
        for (int i = 1; i <= 5; i++) {
            sb.append("item").append(i);
            if (i < 5) sb.append(", ");
        }
        System.out.println(sb.toString()); // "item1, item2, item3, item4, item5"
        sb.reverse();
        System.out.println(sb.toString());

// Block scope demo
        int outer = 10;
        {
            int inner = 20; // only visible inside this block
            System.out.println("inner + outer = " + (inner + outer));
        }
        // System.out.println(inner); // compile error — inner is out of scope
        System.out.println("MAX_ITEMS = " + MAX_ITEMS);
        System.out.println("label = " + label);
    }

public static void main(String[] args) {
        new StringsAndScope("demo").demonstrateStrings();
    }
}