Socket communication in Java enables communication between two endpoints over a network. There are two main types of sockets: TCP sockets and UDP sockets. Let's explain both types with examples: TCP Socket Communication: 1. **Server Side**: - The server creates a `ServerSocket` object to listen for incoming connections on a specific port. - When a client connects, the server accepts the connection and creates a `Socket` object to communicate with the client. - The server reads from and writes to the socket's input and output streams to communicate with the client. import java.io.*; import java.net.*; public class TCPServer { public static void main(String[] args) throws IOException { ServerSocket serverSocket = new ServerSocket(12345); System.out.println("Server started. Waiting for client..."); Socket clientSocket = serverSocket.accept(); ...
String Class and Methods in Java
The `String` class in Java is part of the `java.lang` package and is used to represent a sequence of characters. Strings in Java are immutable, meaning that once a `String` object is created, its value cannot be changed. The `String` class provides various methods to manipulate and perform operations on strings.
1. Creating Strings:
Strings can be created in Java using the following methods:
// Using string literal
String str1 = "Hello, World!";
// Using the new keyword
String str2 = new String("Hello, World!");
2. String Length:
The `length()` method returns the length of the string (number of characters).
String str = "Hello, World!";
int length = str.length(); // Returns 13
3. Concatenation:
The `concat()` method or the `+` operator is used for string concatenation.
String str1 = "Hello";
String str2 = "World";
String result = str1.concat(", ").concat(str2); // or, str1 + ", " + str2
4. Substring:
The `substring()` method is used to extract a portion of the string.
String str = "Hello, World!";
String subStr = str.substring(7); // Returns "World!"
5. String Comparison:
String comparison can be done using the `equals()` method for content comparison and `compareTo()` for lexicographical comparison.
String str1 = "Hello";
String str2 = "World";
boolean isEqual = str1.equals(str2); // Returns false
int result = str1.compareTo(str2); // Returns a negative value
6. Changing Case:
The `toUpperCase()` and `toLowerCase()` methods change the case of the string.
String str = "Hello, World!";
String upperCase = str.toUpperCase(); // Returns "HELLO, WORLD!"
String lowerCase = str.toLowerCase(); // Returns "hello, world!"
7. String Formatting:
The `format()` method is used to format strings similarly to `printf` in C.
String formattedStr = String.format("Value: %d, Text: %s", 42, "Java");
8. Checking Substring:
The `contains()` method checks if a string contains a specified sequence of characters.
String str = "Hello, World!";
boolean containsHello = str.contains("Hello"); // Returns true
9. Trimming Whitespace:
The `trim()` method removes leading and trailing whitespaces.
String str = " Hello, World! ";
String trimmedStr = str.trim(); // Returns "Hello, World!"
10. Converting to Other Types:
The `valueOf()` method is used to convert other data types to strings.
int number = 42;
String str = String.valueOf(number); // Converts int to String
These are some of the commonly used methods provided by the `String` class in Java. Understanding and using these methods effectively will enhance your ability to work with strings in Java.
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