What is String Comparison ?

String class have numbers of methods for comparing strings and portions of strings. Strings can be compare on the basis of content and their references. Below some string class methods which are used to compare strings are :

Modifier and Method Name	Description
boolean endsWith(String suffix) boolean startsWith(String prefix)	Returns true if this string ends with or begins with the substring specified as an argument to the method.
boolean startsWith(String prefix, int offset)	Considers the string beginning at the index offset, and returns true if it begins with the substring specified as an argument.
int compareTo(String anotherString)	Compares two strings lexicographically. Returns an integer indicating whether this string is greater than (result is > 0), equal to (result is = 0), or less than (result is < 0) the argument.
int compareToIgnoreCase(String str)	Compares two strings lexicographically, ignoring differences in case. Returns an integer indicating whether this string is greater than (result is > 0), equal to (result is = 0), or less than (result is < 0) the argument.
boolean equals(Object anObject)	Returns true if and only if the argument is a String object that represents the same sequence of characters as this object.
boolean equalsIgnoreCase(String anotherString)	Returns true if and only if the argument is a String object that represents the same sequence of characters as this object, ignoring differences in case.
boolean matches(String regex)	Tests whether this string matches the specified regular expression.

1) String Comparison using equals() method

this method compares two strings content

String s1 = "pushkar";
String s2 = "pushkar";  
System.out.println(s1.equals(s2));

It will print true because both strings s1 and s2 have same content.

2) String Comparison using equalsIgnoreCase() method

this method compares two strings content weather, it's in uppercase or lowercase, but both strings contains same sequence of characters .

String s1 = "pushkar";
String s2 = "PUSHKAR";
System.out.println(s1.equalsIgnoreCase(s2));

It will print true because this method will ignore case.

3) String Comparison using == operator

The == operator is used to compare two strings references not their content. Here references means their memory addresses, weather they belongs to same memory or not. Because Java uses two memory locations to store Strings i.e all the String literals are store in StringConstantPool and Strings created with new operator are store in Heap memory.

String s1 = "pushkar";
String s2 = "pushkar";
System.out.println(s1 == s2); // Line 1
String s3 = new String("pushkar");
System.out.println(s2 == s3); // Line 2

Line 1 will print true because both refer to same reference.

Line 2 will print false because both have different memory references.

4) String Comparison using compareTo() method

This method return integer values i.e. 0,1 and -1. Suppose we have two strings s1 and s2 and if s1 == s2 it will return 0, if s1 > s2 it will return 1 and if s1 < s2 it will return -1.

String s1 = "pushkar";
String s2 = "pushkar";
String s3 = "pushkara";
  
System.out.println(s1.compareTo(s2)); //it will print 0
System.out.println(s3.compareTo(s1)); //it will print 1
System.out.println(s1.compareTo(s3)); //it will print -1

      

Blog Author - Pushkar Khosla,
Software Developer by Profession with 3.0 Yrs of Experience , through this blog i'am sharing my industrial Java Knowledge to entire world. For any question or query any one can comment below or mail me at pushkar.itsitm52@gmail.com.

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