Scanner
The Scanner class is part of the java.util package and primarily used to read in inputs from a variety of different sources, such as input streams, users, files, etc.
Method Details
Scanner
public Scanner(System.in)
Creates a Scanner object to read input entered by a user in the console.
Parameters
| Name | Type | Description |
|---|---|---|
| System.in | InputStream | take inputs from the standard input (i.e., the keyboard) |
Examples
Scanner input = new Scanner(System.in);
Scanner
public Scanner(File source)
Creates a Scanner object to read the contents of the specified File object.
Parameters
| Name | Type | Description |
|---|---|---|
| source | File | Input is of the type |
Examples
Scanner fileReader = new Scanner(File source);
close
public void close()
This method closes a Scanner object that has been opened.
Examples
Scanner input = new Scanner(System.in);
System.out.println("Say something: " + input.nextLine());
input.close(); // close the Scanner object
hasNext
public boolean hasNext()
The hasNext() method returns true if the Scanner has another token in its input.
Examples
File myFile = new File("samplefile.txt");
// create Scanner object with the file
Scanner fileReader = new Scanner(myFile);
// check if the Scanner object has a token to read
System.out.println("Result: " + fileReader.hasNext());
// print the contents
System.out.println("File contents: " + fileReader.next());
fileReader.close();
Output:
Result: true
File contents: Hello
hasNextBoolean
public boolean hasNextBoolean()
The hasNextBoolean() method returns true if the next token in the Scanner object is a boolean.
Examples
File myFile = new File("samplefile.txt");
// create a new Scanner object to read the file
Scanner fileReader = new Scanner(myFile);
// check if the Scanner's next token is a boolean
System.out.print(fileReader.hasNextBoolean());
System.out.print(" -> " + fileReader.nextBoolean() + "\n");
fileReader.close();
Output:
true -> false
hasNextDouble
public boolean hasNextDouble()
The hasNextDouble() method is used to determine if the next token in the Scanner object's input can be interpreted as a double. It will return true if the Scanner object's input can be interpreted as a double, otherwise returns false.
Examples
if (input.hasNextDouble()) {
System.out.println("Identified a double" + input.nextDouble());
}
input.close();
hasNextInt
public boolean hasNextInt()
The hasNextInt() method is used to determine if the next token in the Scanner object's input can be interpreted as an int. It will return true if the Scanner object's input can be interpreted as an int, otherwise returns false.
Examples
if (hasNextInt()) {
System.out.println("Identified an int object" + input.nextInt());
}
input.close();
hasNextLine
public boolean hasNextLine()
The hasNextLine() method returns true if the Scanner input object has another line of input.
Examples
File myFile = new File("samplefile.txt");
Scanner fileReader = new Scanner(myFile);
while (fileReader.hasNextLine()) {
System.out.println(fileReader.nextLine());
}
fileReader.close();
next
public String next()
The next() method finds the next token from the Scanner input object and returns it.
Examples
Scanner input = new Scanner(System.in);
System.out.print("Enter your first name: ");
// read in the input
String firstName = input.next();
// print the value read by the Scanner object
System.out.println("First name is: "+ firstName);
input.close();
nextBoolean
public boolean nextBoolean()
The nextBoolean() method scans the input as a boolean value and then returns that value. If the next value in the input cannot be translated into a valid boolean value, it will throw an InputMismatchException.
Examples
if (input.hasNextBoolean()) {
System.out.println("Found a boolean :" + input.nextBoolean());
}
input.close();
nextDouble
public double nextDouble()
The nextDouble() method reads the input as a double value and then returns that value. If the next value in the input cannot be translated into a valid double value, it will throw an InputMismatchException.
Examples
if (input.hasNextDouble()) {
System.out.println("Found double value :" + input.nextDouble());
}
input.close();
nextInt
public int nextInt()
The nextInt() method reads the input as an int value and then returns that value. If the next value in the input cannot be translated into a valid int value, it will throw an InputMismatchException.
Examples
if (input.hasNextInt()) {
System.out.println("Found int value: " + input.nextInt());
}
input.close();
nextLine
public String nextLine()
The nextLine() method reads the contents of the user input or a file until a new line is encountered.
Examples
File myFile = new File("samplefile.txt");
Scanner fileReader = new Scanner(myFile);
System.out.println(fileReader.nextLine());
fileReader.close();
