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Arrays & Strings in Java – Organize and Manipulate Data · devs3

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#java #programming #core-java #java-arrays #java-strings #string-builder #beginner-java

Arrays & Strings in Java – Organize and Manipulate Data

By SM · February 17, 2026 · 3 min read · 180 views

Introduction

In previous article, we learned control flow statements: if-else, switch, and loops.

Now, in this article, we’ll focus on storing and managing multiple pieces of data using:

Arrays – for collections of similar items
Strings – for text manipulation
StringBuilder & StringBuffer – for efficient string operations

By the end of this article, you’ll be able to store, access, and modify data effectively in Java programs.

1️⃣ Arrays in Java

An array is a container that stores multiple values of the same type in a single variable.

Syntax

java

dataType[] arrayName = new dataType[size];

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| Method                                      | Description                   | Example                          |
| ------------------------------------------- | ----------------------------- | -------------------------------- |
| length()                                    | Get number of characters      | `"Java".length()` → 4            |
| charAt(int index)                           | Character at position         | `"Java".charAt(1)` → a           |
| toUpperCase()                               | Convert to uppercase          | `"java".toUpperCase()` → JAVA    |
| toLowerCase()                               | Convert to lowercase          | `"JAVA".toLowerCase()` → java    |
| substring(int start, int end)               | Extract substring             | `"Hello".substring(1,4)` → ell   |
| contains(CharSequence s)                    | Check if string contains text | `"Java".contains("va")` → true   |
| replace(CharSequence old, CharSequence new) | Replace characters            | `"Java".replace("a","o")` → Jovo |

java

StringBuilder sb = new StringBuilder("Hello");
sb.append(" World");
System.out.println(sb); // Hello World
sb.insert(6, "Java ");
System.out.println(sb); // Hello Java World
sb.reverse();
System.out.println(sb); // dlroW avaJ olleH

java

public class StudentsExample {
    public static void main(String[] args) {
        String[] students = {"Rahim", "Karim", "Selim"};

        // Print all students
        for(String student : students) {
            System.out.println(student);
        }

        // Append " - Passed" to each name using StringBuilder
        for(String student : students) {
            StringBuilder sb = new StringBuilder(student);
            sb.append(" - Passed");
            System.out.println(sb);
        }
    }
}

Arrays & Strings in Java – Organize and Manipulate Data

Introduction

1️⃣ Arrays in Java

Syntax

Join the conversation

Comments

Java Spring Boot Http request cycle

Java spring boot development environment setup process step by step for windows 11

Example:

Declare and Initialize in One Line

Access Array Elements

Modify Array Elements

Array Length

Loop Through an Array

2️⃣ Multi-Dimensional Arrays

Syntax

Example:

3️⃣ Strings in Java

Example:

Common String Methods

4️⃣ StringBuilder & StringBuffer

Example: StringBuilder

5️⃣ Real-World Example: Student Names

Common Beginner Mistakes

Example: String comparison

Summary

Next Article Preview 👀

Introduction

1️⃣ Arrays in Java

Syntax

Join the conversation

Comments

Keep reading

Java Spring Boot Http request cycle

Java spring boot development environment setup process step by step for windows 11

Example:

Declare and Initialize in One Line

Access Array Elements

Modify Array Elements

Array Length

Loop Through an Array

2️⃣ Multi-Dimensional Arrays

Syntax

Example:

3️⃣ Strings in Java

Example:

Common String Methods

4️⃣ StringBuilder & StringBuffer

Example: StringBuilder

5️⃣ Real-World Example: Student Names

Common Beginner Mistakes

Example: String comparison

Summary

Next Article Preview 👀