Java Tutorial/File/InputStreamReader

Deal with Keyboard Input with BufferedReader

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);
  }
}

Get a class of an object

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;
  }
}

InputStreamReader

1. An InputStreamReader reads bytes and translates them into characters using the specified character set.
2. InputStreamReader is ideal for reading from the output of an OutputStreamWriter or a PrintWriter.

The InputStreamReader class has four constructors:

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)

Reading ISO Latin-1 Encoded Data

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);
  }
}

Uses a PrintWriter to write two Chinese characters and read them back.

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());
    }
  }
}