Java 单字节、多字节读取文本文档中的内容

参考1：Java中try()catch{}的使用方法

参考2：The try-with-resources Statement

文本文档位于工程下，使用鼠标右键点击工程，选择new -> File，即可创建。

文本文档的格式：GBK

例1：单字节读取

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

public class Main {

    public static void main(String[] args) {
        System.out.println(System.getProperty("user.dir"));

        File file = new File("text.txt");
        InputStream inputStream = null;
        
        try {
            if ((file.exists()) && (file.isFile())) {
                inputStream = new FileInputStream(file);
                int data = -1;
                do {
                    data = inputStream.read();
                    if (data != -1) {
                        System.out.print((char) data);
                    } else {
                        System.out.print(data);
                    }
                } while (data != -1);
                System.out.println();
            } else if (!file.exists()) {
                System.out.println("The " + file.getName() + " does not exist.");
            } else if (!file.isFile()) {
                System.out.println("The " + file.getName() + " is not a file.");
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (inputStream != null) {
                    // Closes this input stream and releases any system resources associated with the stream.
                    inputStream.close();
                    System.out.println("Close the input stream.");
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

改写例1：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

public class Main {

    public static void main(String[] args) {
        System.out.println(System.getProperty("user.dir"));

        File file = new File("text.txt");
        
        try (InputStream inputStream = new FileInputStream(file)) {
            if ((file.exists()) && (file.isFile())) {
                int data = -1;
                do {
                    data = inputStream.read();
                    if (data != -1) {
                        System.out.print((char) data);
                    } else {
                        System.out.print(data);
                    }
                } while (data != -1);
                System.out.println();
            } else if (!file.exists()) {
                System.out.println("The " + file.getName() + " does not exist.");
            } else if (!file.isFile()) {
                System.out.println("The " + file.getName() + " is not a file.");
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e1) {
            e1.printStackTrace();
        }
    }
}

多字节读取

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

public class IOTest02 {

    public static void main(String[] args) {
        File src = new File("src.txt");
        InputStream is = null;
        
        try {
            is = new FileInputStream(src);
            byte[] buffer = new byte[1024 * 1];                    // 1k bytes
            int length = -1;
            while ((length = is.read(buffer)) != -1) {
                String str = new String(buffer, 0, length);        // decode
                System.out.print(str);
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (is != null) {
                    is.close();
                    System.out.println("

InputStream Closed.");
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}