chapter19n1.java

JAVA源代码程序aashjkjhkjhkjhjkhkj

/**
 * program to illustrate simple i/o to the user's terminal
 */

import java.io.* ;
import java.lancs.* ;
import java.util.* ;

public class Chapter19n1
    {
    public static void main(String[] args) throws IOException
	{
	// find out what sort of object the standard i/o streams are
	System.out.println("System.in is a " + System.in.getClass().getName()) ;
	System.out.println("System.out is a "
			 + System.out.getClass().getName()) ;
	System.out.println("System.err is a "
			 + System.err.getClass().getName()) ;
	System.out.println() ;

	// simple use of print/ln
	System.out.print("to be or not to be") ;
	System.out.println("that is the question") ;
	System.out.println() ;

	System.out.println("to be or not to be") ;
	System.out.println("that is the question") ;
	System.out.println() ;

	System.out.print("to be or not to be") ;
	System.out.println() ;
	System.out.println("that is the question") ;
	System.out.println() ;

	// indirect use of the "toString" method
	Date now = new Date() ;
	System.out.println("today's date is " + now) ;
	System.out.println() ;

	// output of numerical values
	System.out.println("**" + 123 + "**") ;
	System.out.println("**" + 456 + "**") ;
	System.out.println("**" + (double) 123456789 + "**") ;
	System.out.println("**" + (double) 1.23456 + "**") ;
	System.out.println("**" + (double) 12.3456 + "**") ;
	System.out.println("**" + (double) 123.456 + "**") ;
	System.out.println("**" + (double) 1234.56 + "**") ;
	System.out.println("**" + (double) 12345.6 + "**") ;
	System.out.println("**" + (double) 123.456789 + "**") ;
	System.out.println("**" + (double) 1234567.89 + "**") ;
	System.out.println() ;

	// use of the "flush" method and the "err" stream
	System.err.print("type in an integer value ") ;
	System.err.flush() ;
	int x = BasicIo.readInteger() ;
	System.out.println("the value of " + x + " squared is " + x * x) ;
	System.out.println() ;

        BufferedReader din =
		 new BufferedReader(new InputStreamReader(System.in)) ;
	System.err.println("type in some lines, please") ;
	while (true)
	    {
	    String line = din.readLine() ;
	    if (line == null)
		{
		System.err.println("fell off the end of the file") ;
		break ;
		}
	    line = line.trim() ;
	    if (line.length() == 0)
		break ;
            System.out.println("the line was **" + line + "**") ;
	    }
        System.out.println("**end of input**") ;
	System.out.println() ;

	System.err.println("type in some more lines (in tokens), please") ;
	while (true)
	    {
	    String line = din.readLine().trim() ;
	    if (line.length() == 0)
		break ;
            StringTokenizer st = new StringTokenizer(line) ;
            // StringTokenizer st = new StringTokenizer(line, "|") ;
            // StringTokenizer st = new StringTokenizer(line, " ,.") ;
	    while (st.hasMoreTokens())
	        System.out.println("the token was **" + st.nextToken() + "**") ;
	    }
        System.out.println("**end of input**") ;
	System.out.println() ;

	System.err.println("type an integer followed by a double (2 * i)") ;
	boolean invalidInput = false ;
	int firstValue = 0 ;
        double secondValue = 0.0 ;
	do
	    {
	    String line = din.readLine().trim() ;
	    StringTokenizer st = new StringTokenizer(line) ;
	    try {
		firstValue = Integer.parseInt(st.nextToken()) ;
	        secondValue = Double.valueOf(st.nextToken()).doubleValue() ;
	        invalidInput = !isInputOK(firstValue, secondValue) ;
		}
            catch (NumberFormatException e)
		{
		invalidInput = true ;
		}
            if (invalidInput)
		System.err.println("ERROR: retype both values") ;
	    }
        while (invalidInput) ;
	System.out.println("the first value is " + firstValue) ;
	System.out.println("the second value is " + secondValue) ;
	System.out.println() ;
	} // end of main method

    public static boolean isInputOK(int a, double b)
	{
	return (b == 2 * a) ;
	} // end of method isInputOK
    } // end of class Chapter19n1.java