1. Interactive Standard Input/output
In Java

2. Keyboard Input (prior to 1.5)
System.in object
The connection allowing data entry from the standard input device.
Referred to as the stream object.
Delivers data as a stream of individual bytes.
CSC 331 Object-Oriented Programming Using Java

3. Keyboard Input (prior to 1.5) Classes Methods
InputStream
InputStreamReader
BufferedReader
read()
System.in.read()
Returns the key typed as an integer value.
Object of this class converts from integer to a character value.
readLine()
br.readLine()
Returns as a string the characters typed.
CSC 331 Object-Oriented Programming Using Java

4. Keyboard Input (prior to 1.5)
First, construct InputStreamReader object from System.in object. InputStreamReader isr = new InputStreamReader(System.in);
Next, construct a BufferedReader stream object. BufferedReader br = new BufferedReader(isr);
Now, br.readLine() can be used to read a string.
Example: String s1 = br.readLine();
CSC 331 Object-Oriented Programming Using Java

5. Additional Requirements for Keyboard Input (prior to 1.5)
Use appropriate import statement to access input stream classes: import java.io.*;
Include throws java.io.IOException when using readline().
See KeyboardInput.java
CSC 331 Object-Oriented Programming Using Java

6. The StringTokenizer class
Enables readLine() to accept multiple strings that can be converted to numeric values.
Requires import java.util.*;
CSC 331 Object-Oriented Programming Using Java

7. Useful Wrapper Class Conversion Routines
Integer.parseInt(string) – returns integer val.
Integer.parseLong(string) – returns long val.
Float.parseFloat(string) – returns float val.
Double.parseDouble(string) – returns double
There is a toString(arg) method for each of these, e.g.,
Float.toString( ) returns “ ”
CSC 331 Object-Oriented Programming Using Java

8. Keyboard Input using Scanner(1.5)
First, construct Scanner object from System.in object. Scanner scannerObject = new Scanner(System.in);
Next, use Scanner methods as appropriate to read integers: int n1=scannerObject.nextInt(); doubles: double d1=scannerObject.nextDouble(); and so on.
Now, scannerObject.nextLine(); can be used to read a string.
Example: String line = scannerObject.nextLine();
See KeyboardScanner.java.
CSC 331 Object-Oriented Programming Using Java

9. Formatted Output (before 1.5)
Use the format() method from java.text.DecimalFormat
Three requirements:
1. import java.text.*;
2. Include a statement that uses new to create the desired format string.
3. Use a call to format() to apply the format string to a numerical value.
CSC 331 Object-Oriented Programming Using Java

10. Symbols for User-Defined Format Strings Symbol Description# . , ; %
Digit placeholder/
Digit placeholder & automatic fill character.
Decimal placeholder
Grouping separator.
Separate positive & negative format strings.
Multiply by 100 & add a % sign.
CSC 331 Object-Oriented Programming Using Java

11. CSC 331 Object-Oriented Programming Using Java
Example (before 1.5):
import java.text.*;
public class WithFormats{
public static void main (String[ ] args){
DecimalFormat num= new DecimalFormat(“000”);
System.out.println(num.format(6));
System.out.println(num.format(18));
System.out.println(num.format(124));
System.out.println(“---”);
System.out.println(num.format( )); }
CSC 331 Object-Oriented Programming Using Java

12. CSC 331 Object-Oriented Programming Using Java
The class Formatter (1.5)
Operates similarly to C++ printf();
See Head First Java text, pp
CSC 331 Object-Oriented Programming Using Java

13. CSC 331 Object-Oriented Programming Using Java
The method printf() (1.5)
Operates similarly to C++ printf();
Added to the PrintStream class.
Example:
double price = 19.8; System.out.print(“$”); System.out.printf(“%6.2f”,price); // no new line Produces: $ 19.80
CSC 331 Object-Oriented Programming Using Java

14. GUI Interactive User Input/Output
JOptionPane.showInputDialog(string);
JOptionPane.showMessageDialog(
CSC 331 Object-Oriented Programming Using Java

15. CSC 331 Object-Oriented Programming Using Java
Conclusion
Java is continually being updated.
Many enhancements are aimed at making it easier for programmers to use.
CSC 331 Object-Oriented Programming Using Java