Impara Working with Strings | Reference Types and Strings

Strings in Java are objects that represent sequences of characters. The String class is one of the most commonly used classes in Java, and it provides a rich set of methods for manipulating text. One important feature of the String class is its immutability: once a String object is created, its value cannot be changed. When you modify a string, such as by concatenation or replacement, a new String object is created instead of altering the original.

When you create a string literal, such as "hello", Java stores it in a special area of memory called the string pool. If another string literal with the same value is created, Java will reuse the existing object from the pool rather than creating a new one. This behavior improves memory efficiency and allows for faster comparisons using the == operator when two references point to the same pooled object. However, for comparing the actual contents of two strings, you should use the equals() method, as the == operator only checks if two references point to the same object, not whether their contents are identical.

Main.java


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package com.example;

public class Main {
    public static void main(String[] args) {
        String greeting = "Hello";
        String name = "Alice";
        // Concatenation
        String message = greeting + ", " + name + "!";
        System.out.println(message); // Prints: Hello, Alice!

        // Substring extraction
        String sub = message.substring(7, 12);
        System.out.println(sub); // Prints: Alice

        // Comparison using equals()
        String anotherName = "Alice";
        System.out.println(name == anotherName); // May print: true
        System.out.println(name.equals(anotherName)); // Always prints: true

        // Comparing strings created with new
        String newName = new String("Alice");
        System.out.println(name == newName); // Prints: false
        System.out.println(name.equals(newName)); // Prints: true
    }
}

1. Which statement about string immutability in Java is correct?

2. What is the correct way to compare two strings for equality in Java?

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Sezione 2. Capitolo 2

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