Input / output

With the help of I/O routines the programmer can interact with the program. Among other things, he can query the program status or control the program flow with inputs. The simplest screen output is handled in Java as follows:
System.out.print() or System.out.println()

Variables can be appended to the output string using the + operator.

Output in Java

public class OutputStream {
	public static void main(String[] args) {
		System.out.print("Output ");
		System.out.println("stream");
		System.out.println("new line");
		System.out.printf("new line\n");
		System.out.println(4 + 5);
		System.out.println("Number: " + 6);
	}
}

Output

Output stream
new line
new line
9
Number: 6

Example java output

Code Explanation

public class OutputStream {
	public static void main(String[] args) {
		int a = 2, b = 4;

		System.out.println("First number " + a + ", second number: " + b);
	}
}

Output

First number 2, second number: 4

Input in Java

With the help of the java Scanner class screen inputs can be read in Java. By creating an object of the Scanner class, you have the possibility to take the input value of certain data types over this object. If an object of the Scanner class is no longer needed, it should be closed with the close() method. Otherwise, a memory space is reserved until the end of the program.

Scanner input = new Scanner(System.in);

int val = input.nextInt();
String str = input.next();
char c = input.next().charAt(2);
double d = input.nextDouble();
float f = input.nextFloat();
boolean b = input.nextBoolean();
...

Example java input

Code Explanation

import java.util.Scanner;

public class InputStream {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		int val = input.nextInt();

		System.out.println("Entered value: " + val);
	}
}

Output

5
Entered value: 5

Mixed Example

Code Explanation

import java.util.Scanner;

public class InputOutput {
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		int a, b, result;

		System.out.print("Please enter first number: ");
		a = input.nextInt();

		System.out.print("Please enter second number: ");
		b = input.nextInt();

		input.close();

		result = a + b;

		System.out.println(a + " + " + b + " = " + result);
	}
}

Output

Please enter first number: 5
Please enter second number: 8
5 + 8 = 13