Compare Strings

To compare the equalities of strings, Java provides various methods to help us do so.

Using .equals()

String myStr1 = "Hello";
String myStr2 = "Hello";
String myStr3 = "Another String";
System.out.println(myStr1.equals(myStr2)); // Returns true because they are equal
System.out.println(myStr1.equals(myStr3)); // false

In Java, the .equals() method is used to compare the contents (values) of two strings to determine if they are equal.

When you use .equals() to compare strings, it checks whether the character sequences within the two string objects are identical.

This means that if the characters in both strings are the same and appear in the same order, the .equals() method returns true, indicating that the strings are equal; otherwise, it returns false.

Using .comparesTo()

String myStr1 = "Hello";
String myStr2 = "Hello";
System.out.println(myStr1.compareTo(myStr2)); // Returns 0 because they are equal

In Java, the .compareTo() method is used to compare strings lexicographically (i.e., in dictionary order) to determine their relative ordering.

This method is available in the java.lang.String class and returns an integer value that indicates the comparison result.

The .compareTo() method has the following signature:

int compareTo(String anotherString)

• It takes another string (anotherString) as its argument.

• It returns an integer value, which can have one of three possible outcomes:

  • If the calling string (the one on which .compareTo() is invoked) is lexicographically less than the anotherString, it returns a negative integer.

  • If the calling string is lexicographically greater than the anotherString, it returns a positive integer.

  • If the calling string and anotherString are lexicographically equal, it returns 0.

Lexicographic Ordering:

• "apple" comes before "banana" because 'a' comes before 'b' in the Unicode character set.

• "apple" comes after "app" because 'l' comes after 'p,' and the length of "apple" is greater than "app."

• "Apple" comes before "apple" because 'A' comes before 'a' in the Unicode character set.

• "apple" comes before "Applesauce" because "apple" is shorter and is a prefix of "Applesauce."