Download Lesson 7…. Input from the Keyboard

7-1
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We will consider how to input from the keyboard the three data types…. LQW, GRXEOH, and 6WULQJ.
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Use the QH[W,QW method to input an LQWHJHU from the keyboard:
import java.io.*; //VHH³,PSRUWVQHFHVVDU\´RQQH[WSDJH
import java.util.*;
public class Tester
{
public static void main( String args[] )
{
Scanner kbReader = new Scanner(System.in); //VHH³0\VWHULRXV
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System.out.print(“Enter your integer here. ”); //enter int i = kbReader.nextInt( );
System.out.println(3 * i); //prints
}
}
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Use the QH[W'RXEOH method to input a GRXEOH from the keyboard:
import java.io.*;
import java.util.*;
public class Tester
{
public static void main( String args[] )
{
Scanner kbReader = new Scanner(System.in);
System.out.print(“Enter your decimal number here. ”); //
double d = kbReader.nextDouble( );
System.out.println( 3 * d ); //prints
}
}
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Use the QH[W method to input a 6WULQJ from the keyboard:
import java.io.*;
import java.util.*;
public class Tester{
public static void main( String args[] )
{
Scanner kbReader = new Scanner(System.in);
System.out.print(“Enter your String here. ”); //Enter 2QH7ZR
String s = kbReader.next( ); //inputs up to first white space
System.out.println( “This is the first part of the String,… ” + s);
s = kbReader.next( );
System.out.println( “This is the next part of the String,… ” + s);
}
}
7-2
Output would be as shown below:
Enter your String here. One Two
This is first part of the String,... One
This is next part of the String,... Two
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In a similar way QH[W,QW and QH[W'RXEOH can be used multiple times to parse data
input from the keyboard. For example, if is input from the keyboard, then
QH[W,QW can be applied four times to access these four integers separated by white space.
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Inputting a 6WULQJ (it could contain spaces) from the keyboard using QH[W/LQH:
import java.io.*;
import java.util.*;
public class Tester
{
public static void main( String args[] )
{
Scanner kbReader = new Scanner(System.in);
System.out.print(“Enter your String here. ”); //Enter 2QH7ZR
String s= kbReader.nextLine( );
System.out.println( “This is my string,… ” + s);
}
}
Output would be as shown below:
Enter your String here. One Two
This is my string,... One Two
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We must LPSRUW two classes,….MDYDLRDQGMDYDXWLO that provide methods for
inputting integers, GRXEOHs, and 6WULQJs. See Appendix I for more on the meaning of
“importing”.
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In the above three examples we used the following code:
Scanner kbReader = new Scanner(System.in);
It simply creates the keyboard reader REMHFW (we arbitrarily named it NE5HDGHU)
that provides access to the QH[W,QW, QH[W'RXEOH, QH[W, and QH[W/LQH
methods. For now just accept the necessity of all this…it will all be explained
later.
The 6FDQQHU class used here to create our keyboard reader object only applies
to1.5.0_xx or higher versions of Java. For older versions, see Appendix M for an
alternate way to obtain keyboard input.
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Project… Going in Circles
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Radius of your circle is 139.4.
Project… What’s My Name?
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What is your first name? Cosmo
What is your last name? Kramer
Your full name is Cosmo Kramer.