Strings Manipulation in Java

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We are going through the fundamentals of Java as it is needed for the scripting of Selenium. Java is a very vast language but we will limit our scope to learn basic Java required for scripting in Selenium like Operators, Strings, Decision Making, Loops, Class and Objects, Constructors, Arrays, Access Modifiers. In this blog, we will cover the below mentioned topics:-

1) What is String?
2) Various Functions in String 

  •  length()
  •  concatenation() 
  •  equals()
  •  equalsIgnoreCase()
  •  charAt()
  •  toLowerCase()
  •  toUpperCase()
  •  trim()
  •  replace()
  •  splits()
  •  startsWith()
  •  indexOf()
  •  lastIndexOf
  •  substring() 
  •  contains

  What is String?

String is a class not any data type like int & char.

String is use for storing text. String is an immutable object that means it is constant and cannot change once created.

  A String contains a collection of characters surrounded by double quotes:

  String greeting = “Hello”;

  String store first character at position 0. So, here H is at position 0 and o is at  4

  H     e     l     l     o

  0     1     2    3     4

public class String_Demo {
       public static void main(String[] args) { 

              //creating string by java string literal
              String str1 = "learn";
              char[] message = {'b','a','s','i','c'};

              //creating string by new keyword
              String str2 = new String(message);
              String str3 = new String("java");
              System.out.println(str1);
              System.out.println(str2);
              System.out.println(str3);
       }
   }
 
  Output
  learn
  basic
  java

 Java String Manipulation

     1.  length() : returns the number of characters in the string. It count every alphanumeric char, special char or even spaces.

   public class String_Demo {
       public static void main(String[] args)  {
              String message = "Learn Basic Java";
              int Str_Len= message.length();
              System.out.println("Length of String is : " + Str_Len);   
       }            
   }

  Output
   Length of String is : 16

2.   Concatenation: The + operator can be used between strings to add them together to make a new string. This called concatenation. You can also use this method to concatenate two strings.Java uses the + operator for both addition and concatenation.

 Numbers are add. Strings are concatenated.

public class String_Demo {
       public static void main(String[] args) {
              String message_1 = "Learn Basic Java";
              String message_2 = "and Learn Selenium";
              String  Concat_message= message_1 +" "+ message_2;
              System.out.println("Concatenation Result is : " + Concat_message);
       }
  }

Output
Concatenation Result is : Learn Basic Java and Learn Selenium

3.   equals() – compares two strings lexicographically, ignoring case differences.

 public class String_Demo {
       public static void main(String[] args) {
              String message_1 = "Learn Basic Java";
              String message_2 = "Learn Selenium";
              boolean CompareResult = message_1.equals(message_2);
              System.out.println("The result of String Comparison is : " + CompareResult);
         }
   }

  Output
  The result of String Comparison is : false

4.   equalsIgnoreCase()  – compares two strings lexicographically, ignoring case differences.

public class String_Demo {
	public static void main(String[] args) {
		String message_1 = "selenium";
		String message_2 = "SELENIUM";
		boolean comp_ignore_case = message_1.equalsIgnoreCase(message_2);
		System.out.println("The result of String Comparison after ignoring case difference is : " + comp_ignore_case);
	}
}


Output
The result of String Comparison after ignoring case difference is : true

5.   CharAt() – returns the character located at the specified index.

public class String_Demo {
    public static void main(String[] args) {
           String message = "Learn Basic Java";
           char cIndex = message.charAt(6);
           System.out.println("The fifth character of Popular Topic 1 is : " + cIndex);
       }
}

 Output
 The fifth character of Popular Topic 1 is : B

    6.  toLowerCase() – returns the string in lowercase letter.

     public class String_Demo {
    public static void main(String[] args) {
          String message = "Learn Basic Java";
          String lower_case= message.toLowerCase();
          System.out.println("The message in lower case is : " + lower_case);
     }
}

Output
The message in lower case is : learn basic java

7.   toUpperCase() – Converts all of the characters in the String to upper case.

public class String_Demo {
    public static void main(String[] args) {
           String message = "Learn Basic Java";
           String upper_case= message.toUpperCase();
           System.out.println("The message in upper case is : " + upper_case);
      }
 }
 
Output
The message in upper case is : LEARN BASIC JAVA

8.   trim() – This method returns a copy of the string, with leading and trailing whitespace omitted.

public class String_Demo {
    public static void main(String[] args) {
           String message =" Java ";
            int len_1 = message.length();
            System.out.println("Length of message before trimming white spaces is : " + len_1);
            String message_2 = message.trim();
            int len_2 = message_2.length();
            System.out.println("Message after trimming white spaces is : " + message_2+" and length is "+len_2);
       }
  }

Output
 Length of message before trimming white spaces is : 6
 Message after trimming white spaces is : Java and length is 4

9.   replace() –  replaces occurrences of character with a specified new character.

public class String_Demo {
	public static void main(String[] args) {
           String str = "Java";
           System.out.println(str.replace('v','V'));
      }
}

Output 
JaVa

10.   split(String regex) – splits this string against given regular expression and returns a String array.

public class String_Demo {
	public static void main(String[] args) {
		String message = "Learn Basic Java";
		String[] aSplit = message.split("Basic");
		System.out.println("The first part of the array is : " + aSplit[0]);
		System.out.println("The last part of the array is : " + aSplit[1]);
	}
}
 
Output
The first part of the array is : Learn 
The last part of the array is :  Java

11.  startsWith(String prefix) – Tests if the string starts with the specified prefix.  It returns true if the character sequence represented by the argument is a prefix of the character sequence represented by this string; false otherwise.

public class String_Demo {
	public static void main(String[] args) {
		String str = "Java";
		System.out.println("Result is " + str.startsWith("co"));
	}
}

Output
Result is false

12.   indexOf(String str) – Returns the index within this string of the first occurrence of the specified substring.


public class String_Demo {

	public static void main(String[] args) {
		
		String message = "This is an example of a test framework of Selenium";
		int firstIndex = message.indexOf("of");
		System.out.println("The start index is : " + firstIndex);
	}
}


Output
The start index is : 19

  13.  lastIndexOf(String str) – Returns the index within this string of the last occurrence of the specified substring.


public class String_Demo {

	public static void main(String[] args) {
		
		String message = "This is an example of a test framework of Selenium";
		int lastIndex = message.lastIndexOf("of");
		System.out.println("The last index is : " + lastIndex);
	}
}

Output
The last index is : 39

14. substring() – returns a part of the string.

public class String_Demo {
	public static void main(String[] args) {
		String message = "Learn Basic Java";
		String sSubString = message.substring(5, 12);
		System.out.println("The sub string of Popular Topic 1 from index 5 to 11 is : " + sSubString);
	}
}

Output
The sub string of Popular Topic 1 from index 5 to 11 is :  Basic 

15. contains(CharSequense s) – Returns true if and only if this string contains the specified sequence of char values.


public class String_Demo {

	public static void main(String[] args) {

		String message = "This is an example of a test framework of Selenium";
		boolean containsExample = message.contains("example");
		System.out.println("The string conatins example : " + containsExample);
	}
}

Output
The string conatins example : true

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