Regex for email, phone number, ip address

Author: deepak-malik

README.md

@@ -70,6 +70,7 @@ Implementation of Algorithms in Java, Most of these names are picked up from Gee
 	- [ ] Tower of Hanoi
 
 9. [ ] **Regex**	
-	- [ ] Regex for US Phone Number
-	- [ ] Regex for Email
+	- [X] [Regex for US Phone Number](../master/src/com/deepak/algorithms/Regex/RegexForUSPhoneNumber.java)
+	- [X] [Regex for Email](../master/src/com/deepak/algorithms/Regex/RegexForEmail.java)
+	- [X] [Regex for IP Address](../master/src/com/deepak/algorithms/Regex/RegexForIPAddress.java)
 	- [ ] Regex Pattern Matcher implementation

src/com/deepak/algorithms/Regex/RegexForEmail.java

@@ -1,5 +1,68 @@
+/**
+ * Algorithms-In-Java
+ * RegexForEmail.java
+ */
 package com.deepak.algorithms.Regex;
 
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Regular expression for email address
+ * 
+ * @author Deepak
+ */
 public class RegexForEmail {
 
+	/**
+	 * Method to check for valid email
+	 * 
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		System.out.println(matchEmail("[email protected]")); // true
+		System.out.println(matchEmail("[email protected]")); // true
+		System.out.println(matchEmail("[email protected]")); // true
+		System.out.println(matchEmail("[email protected]")); // true
+		System.out.println(matchEmail("ABC#123$xyz*[email protected]")); // true
+		System.out.println(matchEmail("a [email protected]")); // false
+		System.out.println(matchEmail("[email protected]")); // false
+		System.out.println(matchEmail("[email protected]")); // false
+		System.out.println(matchEmail("@example.com")); // false
+		System.out.println(matchEmail("abc_xyz")); // false
+		System.out.println(matchEmail("email@example..")); // false
+	}
+
+	/**
+	 * Method to check for a valid email address
+	 * Explanation :
+	 * => The local part of email can accept any of these,
+	 * 		Upper case and lower case English alphabets (A-Z, a-z)
+	 * 		Digits 0-9
+	 * 		Characters ! # $ % & ' * + - / = ? ^ _ ` { | } ~
+	 * 		Character . (provided that it is not the first/last character) and it does not appear two or more times consecutively
+	 * 
+	 * Explanation of Regular Expression :
+	 * 
+	 * There will be 4 groups here,
+	 * For groups, we can use [A-Z0-9_!#$%&'*+/=?`{|}~^-]
+	 * ^ - start of the string
+	 * $ - end of the string
+	 * 
+	 * So, first group + any character + second group + @ + third group + any character + fourth group
+	 * first group and second group will be same
+	 * third group and fourth group will be same
+	 * 
+	 * And, we will be using case insensitive here, since we can have A-Z or a-z
+	 * 
+	 * @param input
+	 * @return {@link boolean}
+	 */
+	public static boolean matchEmail(String input) {
+		String regexforEmail = "^[A-Z0-9_!#$%&'*+/=?`{|}~^-]+(?:\\.[A-Z0-9_!#$%&'*+/=?`{|}~^-]+)*@[A-Z0-9-]+(?:\\.[A-Z0-9-]+)*$";
+		Pattern pattern = Pattern.compile(regexforEmail, Pattern.CASE_INSENSITIVE);
+		Matcher matcher = pattern.matcher(input);
+		return matcher.matches();
+	}
+
 }

src/com/deepak/algorithms/Regex/RegexForIPAddress.java

@@ -0,0 +1,67 @@
+/**
+ * Algorithms-In-Java
+ * RegexForIPAddress.java
+ */
+package com.deepak.algorithms.Regex;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Regular expression for IP Address
+ * 
+ * @author Deepak
+ */
+public class RegexForIPAddress {
+
+	/**
+	 * Method to check for valid ip address
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		System.out.println(matchIPAddress("1.1.1.1")); // true
+		System.out.println(matchIPAddress("255.255.255.255")); // true
+		System.out.println(matchIPAddress("192.168.1.1")); // true
+		System.out.println(matchIPAddress("127.0.0.1")); // true
+		System.out.println(matchIPAddress("26.10.2.10")); // true
+		System.out.println(matchIPAddress("10.10.10")); // false
+		System.out.println(matchIPAddress("a.a.a.a")); // false
+		System.out.println(matchIPAddress("999.10.10.20")); // false
+		System.out.println(matchIPAddress("22.2222.22.2")); // false
+		System.out.println(matchIPAddress("127.0.0.310")); // false
+		System.out.println(matchIPAddress("127.0.0.1101")); // false
+	}
+
+	/**
+	 * Method to check for a valid IP Address
+	 * Explanation :
+	 * => A valid IP address will have 4 sets,
+	 * 		[0-255].[0-255].[0-255].[0-255]
+	 * 
+	 * Explanation of Regular Expression :
+	 * 
+	 * There will be 4 groups here,
+	 * ^ - start of the line
+	 * ( - start of group #1
+	 * [01]?\\d\\d? - Can be one or two digits. If three digits appear, it must start either 0 or 1
+	 * e.g ([0-9], [0-9][0-9],[0-1][0-9][0-9])
+	 * | - ...or
+	 * 2[0-4]\\d - start with 2, follow by 0-4 and end with any digit (2[0-4][0-9])
+	 * | - ...or
+	 * 25[0-5] - start with 2, follow by 5 and ends with 0-5 (25[0-5])
+	 * ) - end of group #2
+	 * \. - follow by a dot "."
+	 * .... - repeat with 3 times (3x)
+	 * $ - end of the line
+	 * 
+	 * @param input
+	 * @return {@link boolean}
+	 */
+	public static boolean matchIPAddress(String input) {
+		String regexforIPAddress = "^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])$";
+		Pattern pattern = Pattern.compile(regexforIPAddress);
+		Matcher matcher = pattern.matcher(input);
+		return matcher.matches();
+	}
+
+}

src/com/deepak/algorithms/Regex/RegexForUSPhoneNumber.java

@@ -1,23 +1,57 @@
+/**
+ * Algorithms-In-Java
+ * RegexForUSPhoneNumber.java
+ */
 package com.deepak.algorithms.Regex;
 
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+/**
+ * Regular expression for US Phone Numbers
+ * 
+ * @author Deepak
+ */
 public class RegexForUSPhoneNumber {
-	
+
+	/**
+	 * Main method to test the program 
+	 * 
+	 * @param args
+	 */
 	public static void main(String[] args) {
-		System.out.println(matchUSPhoneNumber("425-633-6014"));
-		System.out.println(matchUSPhoneNumber("425-633-601"));
-		System.out.println(matchUSPhoneNumber("425-6336014"));
-		System.out.println(matchUSPhoneNumber("(425)-633-6014"));
-		System.out.println(matchUSPhoneNumber("42-33-6014"));
-		System.out.println(matchUSPhoneNumber("-633-6014"));
-		System.out.println(matchUSPhoneNumber("6014"));
-		System.out.println(matchUSPhoneNumber("425-633-60145"));
+		System.out.println(matchUSPhoneNumber("4256336014")); // true
+		System.out.println(matchUSPhoneNumber(" 4256336014")); // false
+		System.out.println(matchUSPhoneNumber("425-633-6014")); // true
+		System.out.println(matchUSPhoneNumber("425-633-601")); // false
+		System.out.println(matchUSPhoneNumber("425-6336014")); // true
+		System.out.println(matchUSPhoneNumber("(425)-633-6014")); // true
+		System.out.println(matchUSPhoneNumber("42-33-6014")); // false
+		System.out.println(matchUSPhoneNumber("-633-6014")); // false
+		System.out.println(matchUSPhoneNumber("6014")); // false
+		System.out.println(matchUSPhoneNumber("425-633-60145")); // false
 	}
-	
+
 	/**
 	 * Method to match US phone number 
+	 * Explanation :
+	 * => Phone number can be in below format
+	 * 		1. First part should have 3 digits
+	 * 		2. Second part should have 3 digits
+	 * 		3. Third part should have 4 digits
+	 * => Now, there could be various possibilities in between,
+	 *  i.e we may have a -, a space, no white space or a braces ()
+	 *  
+	 * Explanation of Regular Expression :
+	 * 
+	 * There will be 3 groups since I have 3 different blocks in my input.
+	 * For groups, we can use [0-9]{3} or [0-9]{4}
+	 * ^ - start of the string
+	 * $ - end of the string
+	 * \\ - matches the character literally
+	 * () - capture everything that is enclosed
+	 * ? Quantifier - matches between 0 and 1 times
+	 * [-.\\s] - Match anything out of these
 	 * 
 	 * @param input
 	 * @return {@link boolean}

src/com/deepak/algorithms/Searching/BinarySearch.java

@@ -1,5 +1,5 @@
 /**
- * Algorithms-in-Java
+ * Algorithms-In-Java
  * BinarySearch.java
  */
 package com.deepak.algorithms.Searching;

src/com/deepak/algorithms/Searching/LinearSearch.java

@@ -1,5 +1,5 @@
 /**
- * Algorithms-in-Java
+ * Algorithms-In-Java
  * LinearSearch.java
  */
 package com.deepak.algorithms.Searching;