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Output in Java

Printing output to the console is one of the first things you learn in Java.

System.out Methods

System.out.println() - Prints and adds a newline
System.out.print() - Prints WITHOUT adding newline
System.out.printf() - Formatted output (like printf in C)

Input in Java

Reading user input can be done in multiple ways:

1. Scanner Class (Recommended)

Most commonly used, easy to parse various data types:

2. BufferedReader

Efficient for reading lines of text:

3. Console Class

For interactive console applications:

⚠️ Memory Leak Warning: Always close Scanner/BufferedReader after use with .close() or try-with-resources statement!

Code Examples

Different output methods in Java

java

1// Output examples
2System.out.println("Hello, World!");  // Prints with newline
3System.out.print("No newline");       // No newline
4System.out.println("Next line");      // On new line
5
6// Formatted output
7System.out.printf("Name: %s, Age: %d%n", "John", 25);

Using Scanner for user input (most common approach)

java

1import java.util.Scanner;
2
3Scanner sc = new Scanner(System.in);
4
5System.out.print("Enter your name: ");
6String name = sc.nextLine();  // Read entire line
7
8System.out.print("Enter your age: ");
9int age = sc.nextInt();       // Read integer
10
11System.out.print("Enter height: ");
12double height = sc.nextDouble();  // Read double
13
14sc.close();  // Always close to avoid memory leaks!

Using BufferedReader for efficient line input

java

1import java.io.*;
2
3BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
4
5String line = br.readLine();  // Reads entire line as String
6br.close();

Best practice: using try-with-resources for automatic resource cleanup

java

1// Try-with-resources (automatically closes)
2try (Scanner sc = new Scanner(System.in)) {
3    System.out.print("Enter text: ");
4    String text = sc.nextLine();
5    System.out.println("You entered: " + text);
6}  // Scanner automatically closed here!

Use Cases

Creating interactive console programs
Reading user input for processing
Displaying formatted output to users
Debugging by printing variable values
Creating command-line applications

Common Mistakes to Avoid

Not closing Scanner/BufferedReader (memory leak)
Forgetting to handle InputMismatchException
Mixing nextLine() with nextInt() (causes issues)
Not converting String input to appropriate types
Reading more input than provided by user