How to Get Input from User in Java?

1. Java Scanner Class

The Scanner class is the most widely used input method in Java. The Scanner class is used to read the input of primitive types such as int, double, long, etc., and some non-primitive types such as String, Boolean, etc. 

The input is divided into tokens using a delimiter(which is whitespace by default) by the Scanner class. Methods like nextInt(), next(), nextLine(), nextFloat(), nextBoolean(), etc are used to scan the next token of the input.

The Java Scanner class is present in the Java.util package and has to be imported before using it. It extends the Object class and implements Iterator and Closeable interfaces.

Java Scanner Class Methods

Some of the methods available in the Java Scanner class are:

Example of Java Scanner Class:

• Java

Java

// import Scanner class from java.util package
import java.util.Scanner; 
 
public class Main {
 public static void main(String[] args) {
   // create a Scanner object, sc
   Scanner sc = new Scanner("Input Method in Java"); 
   // check if the scanner has token in the input
   while (sc.hasNext()) {
     // prints the token
     System.out.println(sc.next()); 
   }
   // close the scanner
   sc.close();
 }
}

You can also try this code with Online Java Compiler

Run Code

Output:

Input
Method
in
Java

Advantages of Scanner Class

• It parses the user input and reads it in the desired data type.
• Each word in a string is obtained as a token and handled separately, making string manipulation easier.
• Easier to read data from files.

Disadvantages of Scanner Class

• Buffer size is less (1KB char buffer)
• Not safe for multithreaded programs
• There is ambiguity related to the nextLine() method as Scanner skips nextLine() after the use of any other next method like nextInt().

2. Java Bufferedreader Class

The Java BufferedReader class reads the stream of characters from the character input stream. The BufferedReader class is present in the Java.io package and has to be imported before using it. It inherits the abstract Java Reader Class. This is probably the best input method in Java.

When the buffered character input stream is created, an internal buffer is set automatically. This buffer, by default, has a size of 8KB, which can be changed using the BufferedReader(Reader, int) constructor. While the read operation is performed in BufferedReader.

A chunk of characters is read from the disk and stored in this internal buffer. From this buffer, characters are read one-by-one. This reduces the communication to the disk and makes the BufferedReader fast and efficient.

Java Buffered Reader Class Methods

Some of the methods available in the Buffered Reader class are:

Example of Java Buffered Reader Class:

• Java

Java

// import the classes
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
public class Main {
 public static void main(String[] args) throws IOException {
    InputStreamReader reader = new InputStreamReader(System.in);
    // connect the BufferedReader stream with the InputStreamReader stream to read the line by line data
    BufferedReader br = new BufferedReader(reader);
    // initialize an empty string
    String str="";   
    // continue the loop till the user enters stop
    while(!str.equals("stop")){   
        System.out.println("Enter string: ");  
        // input taken
        str = br.readLine();   
        System.out.println("String: "+str);   
    }             
    br.close();   
    reader.close();   
 }
}

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Output:

Enter string:
Coding
String: Coding
Enter string:
Ninjas
String: Ninjas
Enter string:
Input Method in Java
String: Input Method in Java
Enter string:
stop
String: stop

Must Read Static Blocks In Java.

Advantages of the Bufferedreader Class

• Buffer size is larger (8KB)
   
• It is faster than the Scanner class
   
• No ambiguity related to nextline() method
   
• Buffered Streams are synchronous

Disadvantages of the Bufferedreader Class

• BufferReader and InputStreamReader has to be mentioned
   
• Input passed in string format which has to be parsed into the desired data type

Difference between Scanner Class vs. BufferedReader Class

The difference between the three input methods in Java: Scanner Class, BufferedReader Class, and Console Class are:

Which method to use in Java?

The input method in Java is preferred depending on the requirements of the program. Some of the situations to use a particular method are:-

• The BufferedReader class is preferred to read long strings, as there is a provision to allocate extra buffer size. 
   
• The Scanner class can be used if there is a requirement to parse the input stream with a custom regular expression.

Frequently Asked Questions

What are inputs in Java?

Inputs in Java are data provided by the user during program execution, typically through the keyboard, using classes like Scanner.

What is Java input and output?

Java input and output refer to reading data (input) and displaying results (output), commonly using classes like Scanner and System.out.

How to enter input in Java?

To enter input in Java, use the Scanner class with System.in, then call methods like nextInt() or nextLine() to read data.

What is the best way to take input in Java?

The best way to take input in Java depends on the context. For console-based applications, the Scanner class is convenient. For performance-critical applications, BufferedReader is more efficient.

What is the difference between next() and nextLine() in the Java Scanner Class?

The next() method reads the input till the space character, and the nextLine() method reads the input till the line changes.

What are the three input methods in Java?

Java offers three primary input methods:

1. Using the Scanner class for console-based input.
2. Using the BufferedReader class for efficient buffered input.
3. Utilizing GUI components for graphical input in JavaFX or Swing applications.

How to take two inputs in Java?

To take two inputs in Java, you can use either the Scanner or BufferedReader class. For instance, with Scanner, you can sequentially call appropriate nextInt(), nextDouble(), or other methods to read two inputs. Similarly, with BufferedReader, you can read two lines or tokens as needed.

What is InputMisMatchException Exception in Java?

If the input passed does not match with the method, InputMisMatchException is thrown. For example, if a string is passed using the nextInt() method, the exception would occur.

Conclusion

In this blog, we have discussed how to get input from the user in Java. Obtaining user input in Java is a fundamental aspect of building interactive and dynamic applications. Through the exploration of various input methods like the Scanner and BufferedReader classes, as well as GUI components, we've uncovered versatile approaches to handle user interaction. 

Recommended Readings:

Scanner and nextChar() in Java

Java Scanner Nextdouble() method

InputMisMatchException in Java

BufferedReader Vs Scanner Class In Java