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- Java Programming Examples
- Java Programming Examples
Strings in Java, with examples
A string is a group of characters in Java. Letters, numbers, special characters, and whitespace are all acceptable character types for strings. The "java.lang.String" package in Java represents strings. There are numerous methods for working with strings in the String class.
How do I declare a string in Java?
To declare a string variable in Java, you must use the "String" keyword followed by the variable's name and an optional initial value.
String mystring = "Hello there, I'm Edwin";
We've declared a string variable called mystring and set its value to "Hello there, I'm Edwin"
However, you can also declare a string variable and assign a value to it later in the program. As an example:
String mystring; mystring = "Hello there, I'm Edwin";
Java string example
Consider the following Java program as an example demonstrating the string:
public class StringExample { public static void main(String[] args) { String mystring; mystring = "Hello there, I'm Edwin"; System.out.println("The value of 'mystring': " + mystring); } }
The value of 'mystring': Hello there, I'm Edwin
This program declares a "StringExample" class with a single method named "main()." A string variable named "mystring" is declared and initialized with the value "Hello there, I'm Edwin" within the "main" method. The value of the variable "mystring" is then printed to the console using the "System.out.println()" method. Using the "+" operator, the string "The value of 'mystring': " is concatenated with the value of "mystring."
Receive string input
You can also use the "Scanner" class to allow the user to enter the string at run time, store that string value inside a variable, say x," and print the value back on the output console. As an example:
import java.util.Scanner; public class StringExample { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.println("Please enter a string: "); String x = scanner.nextLine(); System.out.println("The value of x is: " + x); } }
Please enter a string: codescracker.com The value of x is: codescracker.com
String concatenation
Either use the "concat()" method or the "+" operator to concatenate two strings in Java. As an example:
public class StringConcatenationExample { public static void main(String[] args) { String str1 = "Codes"; String str2 = "Cracker"; // Using the + operator for concatenation String result1 = str1 + " " + str2; System.out.println("Using + operator: " + result1); // Using the concat() method for concatenation String result2 = str1.concat(" ").concat(str2); System.out.println("Using concat() method: " + result2); } }
Using + operator: Codes Cracker Using concat() method: Codes Cracker
String length
Use the "length()" method to find the length of a string in Java. As an example:
import java.util.Scanner; public class StringLengthExample { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.println("Please enter a string: "); String my_string = scanner.nextLine(); int length = my_string.length(); System.out.println("The length of the string is: " + length); } }
Please enter a string: codescracker dot com The length of the string is: 20
String comparison
Use the "equals()" method when you need to compare two strings in Java. As an example:
import java.util.Scanner; public class StringComparisonExample { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.println("Please enter the first string: "); String a = scanner.nextLine(); System.out.println("Please enter the second string: "); String b = scanner.nextLine(); boolean equal = a.equals(b); if (equal) { System.out.println("\nThe two strings are equal."); } else { System.out.println("\nThe two strings are not equal."); } } }
Please enter the first string: codescracker Please enter the second string: codescracker The two strings are equal.
And if you enter two strings that are not equal, say "codes" and "cracker," you will get the following output.
Please enter the first string: codes Please enter the second string: cracker The two strings are not equal.
Extract substring
Use the "substring()" method if you want to extract some part (a substring) from a given string. As an example:
public class ExtractSubstringExample { public static void main(String[] args) { String originalString = "Hello, World!"; String subString = originalString.substring(7, 12); System.out.println(subString); } }
World
We have a "String" variable "originalString" in this program that contains the string "Hello, World!." To extract a substring from the original string, we use the substring() method. The starting index (inclusive) and ending index (exclusive) of the substring to be extracted are passed to the substring() method.
In this example, we pass the arguments 7 and 12 to the substring() method, indicating that we want to extract a substring beginning at index 7 (the character "W" in "World") and ending at index 11 (which is the last "d" in "World"). The resulting substring is assigned to the variable "subString" and then printed to the console with the println() method.
String formatting
Before closing the discussion on the "string" in Java, I want to include one more example that demonstrates the use of "String.format()".
public class FormatStringExample { public static void main(String[] args) { String my_name = "Edwin"; int my_age = 32; String text = String.format("My name is %s and I am %d years old.", my_name, my_age); System.out.println(text); } }
My name is Edwin and I am 32 years old.
That is, the String.format() method in Java is used to format a string according to a format string and arguments. String.format() returns a string that has been formatted. The most popular format specifiers that can be used with Java's String.format() method are listed in the following table with its brief description:
Format specifier | Description |
---|---|
%d | Formats an integer value. |
%f | Formats a floating-point value. |
%s | Formats a string value. |
%c | Formats a character value. |
%b | Formats a boolean value. |
%t | Formats a date/time value. |
%n | Adds a newline character. |
%e | Formats a floating-point value in scientific notation. |
%x | Formats an integer value in hexadecimal. |
%o | Formats an integer value in octal. |
%h | Formats the hash code of an object. |
%% | Inserts a literal percent sign. |
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