Control Statements

Scanner Class

Scanner is a class that is built-in to Java (starting with Java version 1.5). It is located in the java.util package. Scanner has several methods. Some methods for inputting primitive values are:

• double nextDouble( )
• int nextInt( )

To input Strings you can use:

• String next( ) - returns the next token as a String (stops at a space, tab, or newline)
• String nextLine( ) - returns all input remaining on the line as a String

To check if there are still more tokens left you can use:

• boolean hasNext( )
  It uses End-of-file character
  Ctrl + d UNIX/Linux/MAC
  Ctrl + z Windows
  Close Input button in Netbeans

The following code segment demonstrates all the above methods.

Scanner input = new Scanner(System.in);
int i;
double x;
String word;
String line;
String theRest = "no input";
System.out.print("Enter int, double, word, line: ");
i = input.nextInt();
x = input.nextDouble();
word = input.next(); // returns a String up to next whitespace
line = input.nextLine(); // returns the rest of line , excluding any line separator at the end
System.out.printf("Integer: %d\nDouble: %f\nWord: %s\n Line: %s\n", i, x, word, line);
if (input.hasNext()){
    theRest =  input.nextLine();
}
System.out.printf("Also entered: %s", theRest);

If end-of-file is the next input value after the line, output will be:

Enter int, double, word, line: 4 5.7 Textbook for CSCI201
Integer: 4
Double: 5.700000
Word:
Line: Textbook for CSCI201
end-of-file
Also entered: no input

String API

Complete String API available at http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html. Some methods are:

• charAt( ) - getting the character at a given position within the string;
• indexOf( ) - seeing if a character or string exists within a string;
• length( ) - getting the number of characters in a string;
• substring( ) - extracting a substring from a string;
• toLowerCase( ) - converts all of the characters in a string to lower case;
• toUpperCase( ) - converts all of the characters in a string to upper case.

For example, to make variable alpha equal to the fifth character from String word, you need to write:
  char alpha = word.charAt(4);
Note: Remember that characters are numbered starting at 0, so the fifth character really is at position 4.