我可以在 Java 中的同一个 class 中编写 FileWriter 和 bufferedwriter 吗？

Question

这是我尝试使用 Filewriter 编写的代码。这工作正常。

File f2 = new File("Path");
f2.createNewFile();
FileWriter writing = new FileWriter(f2);    
writing.write("i'm into you , i'm into you");   
writing.flush();

在下面的代码中，我尝试使用 bufferedwriter 来编写。这不是在同一个文件中添加任何文本。对于不同的文件，它正在工作。

BufferedWriter buffwrite = new BufferedWriter(writing);     buffwrite.write("java");    
writing.flush();

Answer 1

这些IO相关class是基于装饰器模式设计的。

如果您参考 BufferedWriter class javadoc，您会发现一个采用 Writer 类型对象的构造函数。 Writer 是一个抽象 class，由 FileWriter 和其他 class 扩展。在构造函数中传递您的 FileWriter 对象，然后调用 BufferedWriter.

的 write (...) 和 flush 方法

所有 IO class都以这种模式工作。

Answer 2

是的你可以write.Please检查以下用例在java中使用FileWriter、BufferedWriter、FileOutputStream和文件在java中写入文件].

package com.journaldev.files;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Paths;

public class WriteFile {

    /**
     * This class shows how to write file in java
     * @param args
     * @throws IOException 
     */
    public static void main(String[] args) {
        String data = "I will write this String to File in Java";
        int noOfLines = 10000;
        writeUsingFileWriter(data);

        writeUsingBufferedWriter(data, noOfLines);

        writeUsingFiles(data);

        writeUsingOutputStream(data);
        System.out.println("DONE");
    }

    /**
     * Use Streams when you are dealing with raw data
     * @param data
     */
    private static void writeUsingOutputStream(String data) {
        OutputStream os = null;
        try {
            os = new FileOutputStream(new File("/Users/pankaj/os.txt"));
            os.write(data.getBytes(), 0, data.length());
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try {
                os.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Use Files class from Java 1.7 to write files, internally uses OutputStream
     * @param data
     */
    private static void writeUsingFiles(String data) {
        try {
            Files.write(Paths.get("/Users/pankaj/files.txt"), data.getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * Use BufferedWriter when number of write operations are more
     * It uses internal buffer to reduce real IO operations and saves time
     * @param data
     * @param noOfLines
     */
    private static void writeUsingBufferedWriter(String data, int noOfLines) {
        File file = new File("/Users/pankaj/BufferedWriter.txt");
        FileWriter fr = null;
        BufferedWriter br = null;
        String dataWithNewLine=data+System.getProperty("line.separator");
        try{
            fr = new FileWriter(file);
            br = new BufferedWriter(fr);
            for(int i = noOfLines; i>0; i--){
                br.write(dataWithNewLine);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            try {
                br.close();
                fr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Use FileWriter when number of write operations are less
     * @param data
     */
    private static void writeUsingFileWriter(String data) {
        File file = new File("/Users/pankaj/FileWriter.txt");
        FileWriter fr = null;
        try {
            fr = new FileWriter(file);
            fr.write(data);
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            //close resources
            try {
                fr.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

Answer 3

是的，您绝对可以将两者写在同一个 class 中。您的代码没有将任何文本添加到同一文件中，因为您在 BufferedWriter 之前刷新 FileWriter。我刚刚按如下方式编辑了您的代码，它运行良好。

File f2 = new File("Path");
f2.createNewFile();
FileWriter writing = new FileWriter(f2);  
writing.write("i'm into you , i'm into you");

BufferedWriter buffwrite = new BufferedWriter(writing); 
buffwrite.write("java"); 

buffwrite.flush();//flush BufferedWriter first followed by FileWriter
writing.flush();

Answer 4

您应该 close 您打开的资源：FileWriter writing 和 BufferedWriter buffwrite。这个(JavaDoc)

Flushes the stream. If the stream has saved any characters from the various write() methods in a buffer, write them immediately to their intended destination. Then, if that destination is another character or byte stream, flush it. Thus one flush() invocation will flush all the buffers in a chain of Writers and OutputStreams.

正确的方法是使用try-resource语句。这将关闭打开的资源。

或者使用 java.nio.file.Files.write 方法进行资源处理。

我可以在 Java 中的同一个 class 中编写 FileWriter 和 bufferedwriter 吗？

Can I write FileWriter and bufferedwriter in a same class in Java?

java

filewriter

bufferedwriter