Java Tutorial/File/InputStreamReader
Содержание
Deal with Keyboard Input with BufferedReader
<source lang="java">
import java.io.BufferedReader; import java.io.InputStreamReader; public class Main {
public static void main(String[] argv) throws Exception {
System.out.print("Enter your name: ");
InputStreamReader reader = new InputStreamReader(System.in);
BufferedReader in = new BufferedReader(reader);
String name = in.readLine();
System.out.println("Hello, " + name + ". Enter three ints...");
int[] values = new int[3];
double sum = 0.0;
for (int i = 0; i < values.length; i++) {
System.out.print("Number " + (i + 1) + ": ");
String temp = in.readLine();
values[i] = Integer.parseInt(temp);
sum += values[i];
}
System.out.println("The average equals " + sum / values.length);
}
}</source>
Get a class of an object
<source lang="java">
import java.util.ArrayList; import java.util.List; public class Main {
public static void main(String[] args) {
Person p = new Person("A");
Animal a = new Animal("B");
Thing t = new Thing("C");
String text = "hello";
Integer number = 1000;
List<Object> list = new ArrayList<Object>();
list.add(p);
list.add(a);
list.add(t);
list.add(text);
list.add(number);
for (int i = 0; i < list.size(); i++) {
Object o = list.get(i);
if (o instanceof Person) {
System.out.println("My name is " + ((Person) o).getName());
} else if (o instanceof Animal) {
System.out.println("I live in " + ((Animal) o).getHabitat());
} else if (o instanceof Thing) {
System.out.println("My color is " + ((Thing) o).getColor());
} else if (o instanceof String) {
System.out.println("My text is " + o.toString());
} else if (o instanceof Integer) {
System.out.println("My value is " + ((Integer) o));
}
}
}
} class Person {
private String name;
public Person(String name) {
this.name = name;
}
public String getName() {
return name;
}
} class Animal {
private String habitat;
public Animal(String habitat) {
this.habitat = habitat;
}
public String getHabitat() {
return habitat;
}
} class Thing {
private String color;
public Thing(String color) {
this.color = color;
}
public String getColor() {
return color;
}
}</source>
InputStreamReader
- An InputStreamReader reads bytes and translates them into characters using the specified character set.
- InputStreamReader is ideal for reading from the output of an OutputStreamWriter or a PrintWriter.
The InputStreamReader class has four constructors:
<source lang="java">
public InputStreamReader (InputStream in) public InputStreamReader (InputStream in, java.nio.charset.Charset cs) public InputStreamReader (InputStream in, java.nio.charset.CharsetDecoder, dec) public InputStreamReader (InputStream in, String charsetName)</source>
Reading ISO Latin-1 Encoded Data
<source lang="java">
import java.io.BufferedReader; import java.io.FileInputStream; import java.io.InputStreamReader; public class Main {
public static void main(String[] argv) throws Exception {
BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream("infilename"),
"8859_1"));
String str = in.readLine();
System.out.println(str);
}
}</source>
Uses a PrintWriter to write two Chinese characters and read them back.
<source lang="java">
import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; public class MainClass {
public static void main(String[] args) {
try {
char[] chars = new char[2];
chars[0] = "\u4F60";
chars[1] = "\u597D";
String encoding = "GB18030";
File textFile = new File("C:\\temp\\myFile.txt");
PrintWriter writer = new PrintWriter(textFile,
encoding);
writer.write(chars);
writer.close();
// read back
InputStreamReader reader = new InputStreamReader(new FileInputStream(textFile), encoding);
char[] chars2 = new char[2];
reader.read(chars2);
System.out.print(chars2[0]);
System.out.print(chars2[1]);
reader.close();
} catch (IOException e) {
System.out.println(e.toString());
}
}
}</source>
