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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 learning basic Java required for scripting in Selenium like Operators, Strings, Decision-Making, Loops, Class and Objects, Constructors, Arrays, and Access Modifiers. In this blog, we will cover the below-mentioned topics:-
Table of Contents
What is String?
String is a class not any data type like int & char.
The string is used for storing text. The string is an immutable object which 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 counts 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 is called concatenation. You can also use this method to concatenate two strings. Java uses the + operator for both addition and concatenation.
Numbers are added. 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()
It 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()
It 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()
It 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()
It returns the string in lowercase letters.
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()
It converts all 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()
It replaces occurrences of a 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)
It splits this string against a 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)
It 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)
It 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()
It 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)
It 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
QA Automation Expert 
Perfect crisp and simple to understand..
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This is very helpful for me as I'm a Java beginner
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