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2010-06-01T05:20:22Z

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в 17:44, 31 мая 2010

2010-05-31T17:44:27Z

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== Creating a Scanner: read from standard input: Scanner conin = new Scanner(System.in) ==



<source lang="java">
import java.util.Scanner;
public class MainClass {
public static void main(String args[]) {
Scanner conin = new Scanner(System.in);
int count = 0;
System.out.println("Enter numbers to average.");
while (conin.hasNext()) {
if (conin.hasNextDouble()) {
System.out.println(conin.nextDouble());
count++;
}
if(count == 3){
System.exit(0);

}
}
}
}</source>



== Creating a Scanner to read from a string ==



<source lang="java">
import java.util.Scanner;
public class MainClass {
public static void main(String args[]) {
String instr = "10 99.88 scanning is easy.";
Scanner conin = new Scanner(instr);
while (conin.hasNext()) {
if (conin.hasNextDouble()) {
System.out.println(conin.nextDouble());
}
}
}
}</source>



<pre class=codeResult>10.0
99.88</pre>

== In general, to use Scanner, follow this procedure ==

<OL><LI>Call one of Scanner"s hasNextXXX methods to see if the input is available</LI><LI>If available, call Scanner"s nextXXX to read the input.</LI><LI>Repeat first two steps.</LI></OL>



<source lang="java">
Scanner conin = new Scanner(System.in);
int i;
// Read a list of integers.
while(conin.hasNextInt()) {
i = conin.nextInt();
// ...
}</source>



== Searching for the specified pattern within the next line of text ==

<OL><LI>String findInLine(Pattern pattern)</LI><LI>String findInLine(String pattern)</LI><LI></LI></OL>
If the pattern is found, the matching token is consumed and returned.
Otherwise, null is returned.



<source lang="java">
import java.util.Scanner;
public class MainClass {
public static void main(String args[]) {
Scanner sc = new Scanner("Name: Tom Age: 28 ID: 77");
sc.findInLine("ID:");
if (sc.hasNext())
System.out.println(sc.next());
else
System.out.println("Error!");
}
}</source>



<pre class=codeResult>77</pre>

== Setting Delimiters for Scanner ==

Scanner defines where a token starts and ends based on a set of delimiters.
The default delimiters are the whitespace characters.
To Change the delimiters
<OL><LI>Scanner: useDelimiter(String pattern)</LI><LI>Scanner: useDelimiter(Pattern pattern)</LI><LI>Pattern is a regular expression that specifies the delimiter set.</LI></OL>
Use Scanner to compute the average of a list of comma-separated values.



<source lang="java">
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
public class MainClass {
public static void main(String args[]) throws IOException {
FileWriter fout = new FileWriter("test.txt");
fout.write("2, 3.4, 5,6, 7.4, 9.1, 10.5, done");
fout.close();
FileReader fin = new FileReader("Test.txt");
Scanner src = new Scanner(fin);
// Set delimiters to space and comma.
// ", *" tells Scanner to match a comma and zero or more spaces as
// delimiters.
src.useDelimiter(", *");
// Read and sum numbers.
while (src.hasNext()) {
if (src.hasNextDouble()) {
System.out.println(src.nextDouble());
} else {
break;
}
}
fin.close();
}
}</source>



<pre class=codeResult>2.0
3.4
5.0
6.0
7.4
9.1
10.5</pre>

== To find within the next count characters ==

<OL><LI>String findWithinHorizon(Pattern pattern, int count)</LI><LI>String findWithinHorizon (String pattern, int count)</LI></OL>
If successful, it returns the matching pattern.
Otherwise, it returns null.
If count is zero, then all input is searched until either a match is
found or the end of input is encountered.



<source lang="java">
import java.util.Scanner;
public class MainClass {
public static void main(String args[]) {
Scanner sc = new Scanner("Name: Tom Age: 28 ID: 77");
sc.findWithinHorizon("ID:",100);
if (sc.hasNext())
System.out.println(sc.next());
else
System.out.println("Error!");
}
}</source>



<pre class=codeResult>Name:</pre>

== To obtain the current delimiter pattern: Pattern delimiter( ) ==



<source lang="java">
import java.io.IOException;
import java.util.Scanner;
public class MainClass {
public static void main(String args[]) throws IOException {
Scanner src = new Scanner("1,2,3,4");
src.useDelimiter(", *");
System.out.println(src.delimiter());
}
}</source>



<pre class=codeResult>, *</pre>

== Using Scanner: the complement of Formatter ==

<OL><LI>It reads formatted input and converts the input into the binary form.</LI><LI>Scanner can read input from the console, a file, a string, or any source that implements the Readable
interface or ReadableByteChannel.</LI><LI>Scanner is packaged in java.util.</LI></OL>
The following sequence creates a Scanner that reads the file test.txt:



<source lang="java">
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
public class MainClass {
public static void main(String args[]) throws IOException {
// Write output to a file.
FileWriter fout = new FileWriter("test.txt");
fout.write("2 3.4 5 6 7.4 9.1 10.5 done");
fout.close();
FileReader fin = new FileReader("Test.txt");
Scanner src = new Scanner(fin);
// Read and sum numbers.
while (src.hasNext()) {
if (src.hasNextDouble()) {
System.out.println(src.nextDouble());
}else{
break;
}
}
fin.close();
}
}</source>



<pre class=codeResult>2.0
3.4
5.0
6.0
7.4
9.1
10.5</pre>

== Using Scanner to read several different unknown types of data ==



<source lang="java">
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;
public class MainClass {
public static void main(String args[]) throws IOException {
// Write output to a file.
FileWriter fout = new FileWriter("test.txt");
fout.write("int: 1 double 1.0 boolean true");
fout.close();
FileReader fin = new FileReader("Test.txt");
Scanner src = new Scanner(fin);
while (src.hasNext()) {
if (src.hasNextInt()) {
System.out.println("int: " + src.nextInt());
} else if (src.hasNextDouble()) {
System.out.println("double: " + src.nextDouble());
} else if (src.hasNextBoolean()) {
System.out.println("boolean: " + src.nextBoolean());
} else {
System.out.println(src.next());
}
}
fin.close();
}
}</source>



<pre class=codeResult>int:
int: 1
double
double: 1.0
boolean
boolean: true</pre>

== Using Scanner to receive user input ==



<source lang="java">
import java.util.Scanner;
public class MainClass{
public static void main(String[] args){
Scanner scanner = new Scanner (System.in);
String s = scanner.next ();

System.out.println(s);
}
}</source>

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Admin: 1 версия

в 17:44, 31 мая 2010