String in Java

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 In Java, a string is a sequence of characters. Strings are objects, which means they are instances of the class java.lang.String.

Here's an example of how to declare a string variable in Java:

java
String myString = "Hello, world!";

In this example, the variable myString is declared as a string and initialized with the value "Hello, world!".

You can perform various operations on strings in Java, such as concatenation, length calculation, and substring extraction. Here are some examples:

java
// Concatenation
String firstName = "John";
String lastName = "Doe";
String fullName = firstName + " " + lastName; // "John Doe"

// Length calculation
String message = "This is a message.";
int length = message.length(); // 18

// Substring extraction
String sentence = "The quick brown fox jumps over the lazy dog.";
String substring = sentence.substring(4, 9); // "quick"

In addition to the basic string manipulation methods, the java.lang.String class provides many other useful methods, such as charAt, indexOf, replace, toLowerCase, toUpperCase, and more.

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