Scanner - input stream representation

Basics

• Java uses Scanner to provide a text view of an input data stream.

Important constructors for creating Scanners

• Suppose s is a String, f is a File, and u is a URL.
  
  
• Scanner stream = new Scanner( System.in );
  • Makes stream a variable giving a Scanner view of standard input.
    
    
• Scanner stream = new Scanner( f );
  • Makes stream a variable giving a Scanner view of the file represented by f.
    
    
• Scanner stream = new Scanner( u.openStream() );
  
  • Makes stream a variable giving a Scanner view of URL u.
    
    
• Scanner stream = new Scanner( s );
  • Makes stream a variable giving a Scanner view of the character string represented by s.
    

Important methods for getting input

• Suppose stream is a Scanner.
  
  
• stream.next() returns the next input value as a String.
  
  
• stream.nextInt() returns the next input value as an int.
  
  
• stream.nextDouble() returns the next input value as a double.
  
  
• stream.nextBoolean() returns the next input value as a boolean.
  
  
• stream.nextLine() returns the remainder of the current input line as a String.

Important methods for determining whether there is more input

• Suppose stream is a Scanner.
  
  
• stream.hasNext() returns a boolean value indicating whether there is any nonblank input left in the input stream.
  
  
• stream.hasNextLine() returns a boolean value indicating whether there is another line of input (i.e., is there an unprocessed new line character).
  
  
• stream.hasNextInt() returns a boolean value indicating whether the next input is integer. If there is no more input, the method returns false.
  
  
• stream.hasNextDouble() returns a boolean value indicating whether the next input is decimal. If there is no more input, the method returns false.
  
  
• stream.hasNextBoolean() returns a boolean value indicating whether the next input is boolean. If there is no more input, the method returns false.