Arun Kumar

Posted on Mar 25

# Complete Guide to Java String Methods (Simple Blog)

📌 Introduction

In Java, a String is one of the most commonly used classes. It represents a sequence of characters. Java provides many built-in methods to perform operations like searching, modifying, comparing, and formatting strings.

🔹 1. Creating a String

String s1 = "Hello";
String s2 = new String("World");

🔹 2. Length of String

String str = "Java";
System.out.println(str.length());  // 4

🔹 3. Convert Case

String str = "java";

System.out.println(str.toUpperCase()); // JAVA
System.out.println(str.toLowerCase()); // java

🔹 4. Character Access

String str = "Java";

System.out.println(str.charAt(0)); // J

🔹 5. Compare Strings

String a = "Java";
String b = "java";

System.out.println(a.equals(b));         // false
System.out.println(a.equalsIgnoreCase(b)); // true

🔹 6. Compare Using compareTo()

String a = "apple";
String b = "banana";

System.out.println(a.compareTo(b)); // negative value

🔹 7. Substring

String str = "HelloWorld";

System.out.println(str.substring(0, 5)); // Hello

🔹 8. Contains

String str = "Java Programming";

System.out.println(str.contains("Java")); // true

🔹 9. StartsWith / EndsWith

String str = "Java Programming";

System.out.println(str.startsWith("Java")); // true
System.out.println(str.endsWith("ing"));    // true

🔹 10. Index Methods

String str = "banana";

System.out.println(str.indexOf('a'));     // 1
System.out.println(str.lastIndexOf('a')); // 5

🔹 11. Replace

String str = "Java";

System.out.println(str.replace('a', 'o')); // Jovo

🔹 12. Trim

String str = "  Hello  ";

System.out.println(str.trim()); // "Hello"

🔹 13. Split

String str = "Java,Python,C++";

String[] arr = str.split(",");

for (String s : arr) {
    System.out.println(s);
}

🔹 14. Join

String result = String.join("-", "Java", "Python", "C++");

System.out.println(result); // Java-Python-C++

🔹 15. Concatenation

String a = "Hello";
String b = "World";

System.out.println(a + " " + b); // Hello World
System.out.println(a.concat(b)); // HelloWorld

🔹 16. isEmpty() and isBlank()

String s1 = "";
String s2 = " ";

System.out.println(s1.isEmpty()); // true
System.out.println(s2.isBlank()); // true

🔹 17. toCharArray()

String str = "Java";

char[] arr = str.toCharArray();

for (char c : arr) {
    System.out.println(c);
}

🔹 18. Value Conversion

int num = 100;

String str = String.valueOf(num);
System.out.println(str); // "100"

🔹 19. Intern Method

String s1 = new String("Java");
String s2 = s1.intern();

System.out.println(s1 == s2); // false

🔹 20. Format

String name = "Arun";
int age = 25;

String result = String.format("Name: %s, Age: %d", name, age);
System.out.println(result);

DEV Community