Runtime Inputs in java

How to use Dynamic Input in Java

Posted on May 31, 2024
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DYNAMIC INPUTS / INTERACTIVE INPUTS / RUNTIME INPUTS

  • It is possible to give values to variables interactively through the keyboard at the time of program execution (Providing values at the time of runtime)
  • Dynamic inputs are done by using stream concepts in java (how to get runtime input in java).

Streams

  • In java, the input and output (I/O) is achieved with help of stream concept
  • Stream is the sequence of bytes (objects)
  • Streams are generally classified as two types like input stream, output stream

Input Streams

  • If bytes flow from device to the main() function, then this process is called input
  • Ex. Keyboard 

Output Streams

  • If bytes flow from main() to device, then this process is called output
  • Ex. Display screen (Monitor) 

Runtime Inputs

  • Java provides several ways to perform dynamic inputs (runtime inputs) namely DataInputStream, BufferedReader, Scanner classes, etc, …

DATAINPUTSTREAM CLASS

  • It is a predefined class and available in java.io.* package
  • It is used to read java primitive data types (Ex. int, float, double, char, string, etc, …) from the input stream in a machine
  • First we need to wrap an input stream (System.in) in a DataInputStream class and then read java primitive types from the DataInputStream. Because it reads data (numbers) instead of bytes

BUILT-IN INSTANCE METHODS OF DATAINPUTSTREAM CLASS

1. read()

  • It is a built-in instance method of DataInputStream class
  • It is used to read a single byte of data from keyboard              
  • Return type : int

2. readLine()

  • Used to read line of text (string) from keyboard
  • It is similar to gets() in c language
  • It is similar to scanf() in c language and cin in c++ language
  • Return type : String

3. readInt()

  • Used to read an integer value
  • Return type: int

4. readFloat()

  • Used to read a float value
  • Return type: float

5. readDouble()

  • Used to read a double value
  • Return type: double

6. readByte()

  • Used to read a byte value
  • Return type: byte

7. readBoolean()

  • Used to read a boolean value
  • Return type: int

8. readChar()

  • Used to read a character value
  • Return type: char

9. read(byte[] obj)

  • It is used to read the number of bytes from the input stream and store them into byte array (byte [])
  • Return type: int

EXAMPLE OF DYNAMIC INPUTS (RUNTIME INPUTS)

1. SOURCE CODE

(JRuntimeInputs.java)

import java.io.*;

public class JRuntimeInputs 

{

    public static void main(String[] args) throws Exception

    {

// local variables declarations

        String name,place;

        int id;

// DataInputStream definition

        DataInputStream ds=new DataInputStream(System.in);

        System.out.println(“———————————“);

        System.out.println(“\tRuntime (Dynamic) Inputs”);

        System.out.println(“———————————“);        

    // read employee id 

        System.out.print(“Enter the Employee Id \t\t: “);

        String sid=ds.readLine();

    // convert string format number to integer number using parse method

        id=Integer.parseInt(sid);

    // read employee name   

        System.out.print(“Enter the Employee Name \t: “);

        name=ds.readLine();

    // read employee place   

        System.out.print(“Enter the Employee Place \t: “);

        place=ds.readLine();

    // print employee details

        System.out.println(“———————————“);   

        System.out.println(“E-Id\t: “+id);

        System.out.println(“E-Name\t: “+name);

        System.out.println(“E-Place\t: “+place);

    }   

}

2. OUTPUT

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