Java Strings

1. Creating Strings

You can create strings using string literals or using the new keyword.

Try example: Online Java Compiler

public class StringCreateDemo {
    public static void main(String[] args) {

        String s1 = "Hello VINAR TECH";
        String s2 = new String("Welcome to Java");

        System.out.println(s1);
        System.out.println(s2);
    }
}

2. Important String Methods

The String class provides many helpful operations for text handling:

• length() - number of characters
• charAt(int index) - character at given index
• substring(start, end) - extract part of string
• equals(String) - compare actual value
• compareTo(String) - alphabetical comparison
• toUpperCase() / toLowerCase()
• trim() - removes leading/trailing spaces
• split(String) - convert string into array

Try example: Online Java Compiler

public class StringMethodsDemo {
    public static void main(String[] args) {

        String txt = "  Hello World from VINAR TECH  ";

        System.out.println("Length: " + txt.length());
        System.out.println("Trimmed: '" + txt.trim() + "'");
        System.out.println("Uppercase: " + txt.toUpperCase());
        System.out.println("Substring (6 to 11): " + txt.substring(6, 11));
        System.out.println("Index of 'World': " + txt.indexOf("World"));

        String[] words = txt.trim().split(" ");
        System.out.println("Words:");
        for (String w : words) {
            System.out.println(w);
        }
    }
}

3. String Comparison

Use equals() for value comparison (recommended). Use == to compare references (memory location).

Try example: Online Java Compiler

public class StringCompareDemo {
    public static void main(String[] args) {

        String a = "VINAR";
        String b = "VINAR";
        String c = new String("VINAR");

        System.out.println("a == b : " + (a == b));      // True (both in string pool)
        System.out.println("a == c : " + (a == c));      // False (different objects)
        System.out.println("a.equals(c) : " + a.equals(c)); // True (same value)
    }
}

4. String Immutability

Each modification creates a new object in memory.

Try example: Online Java Compiler

public class StringImmutableDemo {
    public static void main(String[] args) {

        String s = "Hello";
        System.out.println("Original: " + s);

        s.concat(" VINAR TECH");  // Not stored
        System.out.println("After concat (unchanged): " + s);

        s = s.concat(" VINAR TECH");  
        System.out.println("After storing concat: " + s);
    }
}

5. StringBuilder & StringBuffer

Use when you need mutable strings (frequent modifications).

A. StringBuilder (Faster, Not Thread-Safe)

Try example: Online Java Compiler

public class StringBuilderDemo {
    public static void main(String[] args) {

        StringBuilder sb = new StringBuilder("VINAR");
        sb.append(" TECH Solutions");

        System.out.println(sb);
    }
}

B. StringBuffer (Thread-Safe)

Try example: Online Java Compiler

public class StringBufferDemo {
    public static void main(String[] args) {

        StringBuffer sbf = new StringBuffer("Secure");
        sbf.append(" Operations");

        System.out.println(sbf);
    }
}