How to Compare Strings in Java

In Java, comparing strings can be done using a variety of methods tailored to different needs. Below are the most commonly used methods for comparison:

1. Using `==` operator

   This compares the objects' reference (memory address), not the content.

   ```java
   String str1 = "hello";
   String str2 = "hello";
   System.out.println(str1 == str2); // true, because both refer to the same object in the string pool
   
   String str3 = new String("hello");
   System.out.println(str1 == str3); // false, because str3 refers to a different object
   ```

2. Using `equals()` method

   This compares the content of the strings.

   ```java
   String str1 = "hello";
   String str2 = new String("hello");
   System.out.println(str1.equals(str2)); // true, because their content is the same
   ```

3. Using `equalsIgnoreCase()` method

   This compares the content of the strings, ignoring case differences.

   ```java
   String str1 = "hello";
   String str2 = "HELLO";
   System.out.println(str1.equalsIgnoreCase(str2)); // true, because their content is the same, ignoring case
   ```

4. Using `compareTo()` method

   This method compares two strings lexicographically. It returns:

   • `0` if the strings are equal
   • A negative number if the first string is lexicographically less than the second string
   • A positive number if the first string is lexicographically greater than the second string

   ```java
   String str1 = "apple";
   String str2 = "banana";
   System.out.println(str1.compareTo(str2)); // negative number, because "apple" is less than "banana"
   ```

5. Using `compareToIgnoreCase()` method

   This method compares two strings lexicographically, ignoring case differences.

   ```java
   String str1 = "apple";
   String str2 = "Banana";
   System.out.println(str1.compareToIgnoreCase(str2)); // negative number, because "apple" is less than "Banana" ignoring case
   ```

In Java, string comparison methods vary depending on whether you must compare memory references, content, or lexicographical order and whether case sensitivity matters. Choose the method that best suits your specific needs.