如何将 ArrayList 的字符串写入文本文件？

Question

I want to write an ArrayList<String> into a text file.

The ArrayList is created with the code:

ArrayList arr = new ArrayList();

StringTokenizer st = new StringTokenizer(
    line, ":Mode set - Out of Service In Service");

while(st.hasMoreTokens()){
    arr.add(st.nextToken());    
}

Answer 1

import java.io.FileWriter;
...
FileWriter writer = new FileWriter("output.txt"); 
for(String str: arr) {
  writer.write(str + System.lineSeparator());
}
writer.close();

Answer 2

You can do that with a single line of code nowadays. Create the arrayList and the Path object representing the file where you want to write into:

Path out = Paths.get("output.txt");
List<String> arrayList = new ArrayList<> ( Arrays.asList ( "a" , "b" , "c" ) );

Create the actual file, and fill it with the text in the ArrayList:

Files.write(out,arrayList,Charset.defaultCharset());

Answer 3

I would suggest using FileUtils from Apache Commons IO library.It will create the parent folders of the output file,if they don't exist.while Files.write(out,arrayList,Charset.defaultCharset()); will not do this,throwing exception if the parent directories don't exist.

FileUtils.writeLines(new File("output.txt"), encoding, list);

Answer 4

If you need to create each ArrayList item in a single line then you can use this code

private void createFile(String file, ArrayList<String> arrData)
            throws IOException {
        FileWriter writer = new FileWriter(file + ".txt");
        int size = arrData.size();
        for (int i=0;i<size;i++) {
            String str = arrData.get(i).toString();
            writer.write(str);
            if(i < size-1)**//This prevent creating a blank like at the end of the file**
                writer.write("\n");
        }
        writer.close();
    }

Answer 5

If you want to serialize the ArrayList object to a file so you can read it back in again later use ObjectOuputStream/ObjectInputStream writeObject()/readObject() since ArrayList implementsSerializable . It's not clear to me from your question if you want to do this or just write each individual item. If so then Andrey's answer will do that.

Answer 6

You might use ArrayList overloaded method toString()

String tmp=arr.toString();
PrintWriter pw=new PrintWriter(new FileOutputStream(file));
pw.println(tmp.substring(1,tmp.length()-1));

Answer 7

I think you can also use BufferedWriter:

BufferedWriter writer = new BufferedWriter(new FileWriter(new File("note.txt")));

String stuffToWrite = info;

writer.write(stuffToWrite);

writer.close();

and before that remember too add

import java.io.BufferedWriter;

Answer 8

Write a array list to text file using JAVA

public void writeFile(List<String> listToWrite,String filePath) {

    try {
        FileWriter myWriter = new FileWriter(filePath);
        for (String string : listToWrite) {
            myWriter.write(string);
            myWriter.write("\r\n");
        }
        myWriter.close();
        System.out.println("Successfully wrote to the file.");
    } catch (IOException e) {
        System.out.println("An error occurred.");
        e.printStackTrace();
    }
}