String Comparison

The Java can compare strings in several ways, depending on your specific needs. String comparison is a common task in programming, and Java provides multiple methods for comparing strings. Here are some common techniques:

1. Using equals() Method: The equals() method is used to compare the content of two strings for equality. It returns true if the strings have the same content and false otherwise. This method performs a case-sensitive comparison.

   String str1 = "Hello";
   String str2 = "hello";
   boolean areEqual = str1.equals(str2); // Returns false

2. Using equalsIgnoreCase() Method: The equalsIgnoreCase() method is similar to equals(), but it performs a case-insensitive comparison. It returns true if the strings have the same content, regardless of case.

   String str1 = "Hello";
   String str2 = "hello";
   boolean areEqual = str1.equalsIgnoreCase(str2); // Returns true

3. Using compareTo() Method: The compareTo() method is used for lexicographical comparison of strings. It returns an integer value:

• If the strings are equal, it returns 0.
• If the calling string is lexicographically less than the provided string, it returns a negative value.
• If the calling string is lexicographically greater than the provided string, it returns a positive value.

   String str1 = "apple";
   String str2 = "banana";
   int result = str1.compareTo(str2); // Returns a negative value

4. Using compareToIgnoreCase() Method: The compareToIgnoreCase() method is similar to compareTo(), but it performs a case-insensitive lexicographical comparison.

   String str1 = "apple";
   String str2 = "Banana";
   int result = str1.compareToIgnoreCase(str2); // Returns a positive value

5. Using == Operator: The == operator compares string references. It checks whether two string variables reference the same string object. It is not recommended for content comparison, as it checks object identity, not equality.

   String str1 = "Hello";
   String str2 = "Hello";
   boolean areSame = (str1 == str2); // Returns true

6. Using equals() and equalsIgnoreCase() with null Checks: When comparing strings, it’s essential to handle null values gracefully. You should check for null before using the equals() or equalsIgnoreCase() methods to avoid NullPointerException.

   String str1 = "Hello";
   String str2 = null;
   boolean areEqual = str1 != null && str1.equals(str2); // Safe comparison

7. Using Objects.equals() (Java 7 and later): The Objects.equals() method allows you to safely compare strings, handling null values without causing exceptions.

   String str1 = "Hello";
   String str2 = null;
   boolean areEqual = Objects.equals(str1, str2); // Safe comparison

The choice of string comparison method depends on your specific requirements. If you need to perform case-insensitive comparisons, use equalsIgnoreCase() or compareToIgnoreCase(). If you need lexicographical ordering, use compareTo() or compareToIgnoreCase(). Be cautious when using the == operator for string comparison, as it may not produce the expected results for content comparison.