创建示例文件：

try {
    File file = new File ("c:/new-file.txt");
    if(file.createNewFile()) {
        System.out.println("Successful created!");
    }
    else {
        System.out.println("Failed to create!");
    }
}
catch (IOException e) {
    e.printStackTrace();
}

只有一行！路径和行是字符串

import java.nio.file.Files;
import java.nio.file.Paths;

Files.write(Paths.get(path), lines.getBytes());

Use:

JFileChooser c = new JFileChooser();
c.showOpenDialog(c);
File writeFile = c.getSelectedFile();
String content = "Input the data here to be written to your file";

try {
    FileWriter fw = new FileWriter(writeFile);
    BufferedWriter bw = new BufferedWriter(fw);
    bw.append(content);
    bw.append("hiiiii");
    bw.close();
    fw.close();
}
catch (Exception exc) {
   System.out.println(exc);
}

这里有一个创建或覆盖文件的小示例程序。这是一个长版本，因此可以更容易理解。

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;

public class writer {
    public void writing() {
        try {
            //Whatever the file path is.
            File statText = new File("E:/Java/Reference/bin/images/statsTest.txt");
            FileOutputStream is = new FileOutputStream(statText);
            OutputStreamWriter osw = new OutputStreamWriter(is);    
            Writer w = new BufferedWriter(osw);
            w.write("POTATO!!!");
            w.close();
        } catch (IOException e) {
            System.err.println("Problem writing to the file statsTest.txt");
        }
    }

    public static void main(String[]args) {
        writer write = new writer();
        write.writing();
    }
}

使用Google的Guava库，我们可以创建和写入文件容易地

package com.zetcode.writetofileex;

import com.google.common.io.Files;
import java.io.File;
import java.io.IOException;

public class WriteToFileEx {

    public static void main(String[] args) throws IOException {

        String fileName = "fruits.txt";
        File file = new File(fileName);

        String content = "banana, orange, lemon, apple, plum";

        Files.write(content.getBytes(), file);
    }
}

该示例在项目根目录中创建一个新的fruits.txt文件。

如果我们使用的是Java7及以上版本，并且还知道要添加（附加）到文件中的内容，我们可以使用NIO包中的newBufferedWriter方法。

public static void main(String[] args) {
    Path FILE_PATH = Paths.get("C:/temp", "temp.txt");
    String text = "\n Welcome to Java 8";

    //Writing to the file temp.txt
    try (BufferedWriter writer = Files.newBufferedWriter(FILE_PATH, StandardCharsets.UTF_8, StandardOpenOption.APPEND)) {
        writer.write(text);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

有几点需要注意：

指定字符集编码总是一个好习惯，因此我们在类StandardCharset中有常量。代码使用try with resource语句，其中资源在try之后自动关闭。

虽然OP没有询问，但为了以防万一我们想搜索具有特定关键字的行，例如机密，我们可以使用Java中的流API：

//Reading from the file the first line which contains word "confidential"
try {
    Stream<String> lines = Files.lines(FILE_PATH);
    Optional<String> containsJava = lines.filter(l->l.contains("confidential")).findFirst();
    if(containsJava.isPresent()){
        System.out.println(containsJava.get());
    }
} catch (IOException e) {
    e.printStackTrace();
}