Java –如何将文本追加到文件

红太狼 2023-02-15 05:15 14阅读 0赞

在Java中，我们可以使用`Files.write`和`StandardOpenOption.APPEND`将文本追加到文件中。

try {
    		// Create file if doesn't exist, write to it
    		// If file exist, append it
    		Files.write(Paths.get("app.log"), "Hello World".getBytes(),
    				StandardOpenOption.CREATE, StandardOpenOption.APPEND);
    
    	} catch (IOException x) {
    		//...
    	}

## 1. Files.write ##

将`List`追加到现有文件中。

FileExample.java

package com.mkyong;
    
    import java.io.IOException;
    import java.nio.charset.Charset;
    import java.nio.charset.StandardCharsets;
    import java.nio.file.Files;
    import java.nio.file.Paths;
    import java.nio.file.StandardOpenOption;
    import java.util.Arrays;
    import java.util.List;
    
    public class FileExample {
    
        public static void main(String[] args) {
    
            Charset utf8 = StandardCharsets.UTF_8;
            List<String> list = Arrays.asList("Line 1", "Line 2");
    
            try {
    
                Files.write(Paths.get("app.log"), list, utf8,
                        StandardOpenOption.CREATE, StandardOpenOption.APPEND);
    
            } catch (IOException x) {
                System.err.format("IOException: %s%n", x);
            }
    
        }
    
    }

输出量

第一次运行。

app.log

Line 1
    Line 2

运行第二次。

app.log

Line 1
    Line 2
    Line 1
    Line 2

## 2. BufferedWriter ##

2.1要启用`append`模式， `append` `true`作为第二个参数传递给`FileWriter` 。

BufferedWriterExample.java

package com.mkyong;
    
    import java.io.BufferedWriter;
    import java.io.FileWriter;
    import java.io.IOException;
    import java.util.Arrays;
    import java.util.List;
    
    public class BufferedWriterExample {
    
        public static void main(String[] args) {
    
            List<String> list = Arrays.asList("Line 1", "Line 2");
    
    		// append mode
            try (FileWriter writer = new FileWriter("app.log", true);
                 BufferedWriter bw = new BufferedWriter(writer)) {
    
                for (String s : list) {
                    bw.write(s);
                    bw.write("\n");
                }
    
            } catch (IOException e) {
                System.err.format("IOException: %s%n", e);
            }
    
        }
    }

2.2在JDK 7之前，我们需要手动关闭所有内容。

ClassicBufferedWriterExample.java

package com.mkyong;
    
    import java.io.BufferedWriter;
    import java.io.FileWriter;
    import java.io.IOException;
    
    public class ClassicBufferedWriterExample {
    
        public static void main(String[] args) {
    
            BufferedWriter bw = null;
            FileWriter fw = null;
    
            try {
    
                String content = "Hellow";
    
                fw = new FileWriter("app.log", true);
                bw = new BufferedWriter(fw);
                bw.write(content);
    
            } catch (IOException e) {
                System.err.format("IOException: %s%n", e);
            } finally {
                try {
                    if (bw != null)
                        bw.close();
    
                    if (fw != null)
                        fw.close();
                } catch (IOException ex) {
                    System.err.format("IOException: %s%n", ex);
                }
            }
        }
    }

## 参考文献 ##

*  [Files.write Java文档][Files.write Java]
 *  [BufferedWriter JavaDocs][]
 *  [FileWriter JavaDocs][]
 *  [StandardOpenOption JavaDocs][]
 *  Java –如何创建和写入文件

标签： [附加文件][Link 1] [io][] [Java][] [nio][]

> 翻译自: [https://mkyong.com/java/java-how-to-append-text-to-a-file/][https_mkyong.com_java_java-how-to-append-text-to-a-file]

[Files.write Java]: https://docs.oracle.com/javase/8/docs/api/java/nio/file/Files.html#write-java.nio.file.Path-java.lang.Iterable-java.nio.charset.Charset-java.nio.file.OpenOption...-
[BufferedWriter JavaDocs]: https://docs.oracle.com/javase/8/docs/api/java/io/BufferedWriter.html
[FileWriter JavaDocs]: https://docs.oracle.com/javase/8/docs/api/java/io/FileWriter.html
[StandardOpenOption JavaDocs]: https://docs.oracle.com/javase/8/docs/api/java/nio/file/StandardOpenOption.html
[Link 1]: https://mkyong.com/tag/append-file/
[io]: https://mkyong.com/tag/io/
[Java]: https://mkyong.com/tag/java/
[nio]: https://mkyong.com/tag/nio/
[https_mkyong.com_java_java-how-to-append-text-to-a-file]: https://mkyong.com/java/java-how-to-append-text-to-a-file/