Strings in Java

Lecture 51:-  Strings in Java

In Java, strings are sequences of characters used to represent text. Strings are one of the most commonly used data types in Java, and the java.lang.String class provides many built-in methods to manipulate and work with strings. Strings in Java are immutable, which means that once a string is created, its value cannot be changed. Instead, string manipulation typically involves creating new strings.

Here are some key points about strings in Java:

1. Declaring Strings: To declare a string variable in Java, you can use the following syntax:

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   String str;

   You can also initialize a string variable with a string literal:

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   String message = "Hello, World!";

2. Concatenation: You can concatenate strings using the + operator:

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   String firstName = "John"; String lastName = "Doe"; String fullName = firstName + " " + lastName;

3. Length of a String: The length() method is used to get the number of characters in a string:

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   String text = "Java is awesome!"; int length = text.length(); // length is 16

4. Accessing Characters: You can access individual characters in a string using the charAt() method:

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   String str = "Hello"; char firstChar = str.charAt(0); // firstChar is 'H'

5. Substrings: You can extract substrings from a string using the substring() method:

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   String text = "Hello, World!"; String substring = text.substring(7); // substring is "World!"

6. Comparison: To compare strings for equality, use the equals() method:

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   String str1 = "hello"; String str2 = "Hello"; boolean isEqual = str1.equals(str2); // isEqual is false

   To perform a case-insensitive comparison, use equalsIgnoreCase().

7. String Manipulation: The String class provides various methods for string manipulation, such as toUpperCase(), toLowerCase(), trim(), replace(), split(), etc.
8. String Formatting: You can format strings using the String.format() method or by using the + operator with placeholders.
9. StringBuilder and StringBuffer: For efficient string concatenation and manipulation, especially in loops, consider using StringBuilder (for single-threaded applications) or StringBuffer (for multi-threaded applications) to avoid unnecessary string object creation.

Strings are a fundamental part of Java programming, and their manipulation is crucial in many applications. Always remember that since strings are immutable, any manipulation creates a new string, so it's important to use StringBuilder or StringBuffer when performance is a concern.