在现有文件中追加字符串的Java程序

在Java中，我们可以使用 FileWriter 在现有文件中附加一个字符串，该文件具有以附加模式打开文件的选项。 Java FileWriter 类用于将面向字符的数据写入文件。它是一个面向字符的类，用于Java中的文件处理。与 FileOutputStream 类不同，我们不需要将字符串转换为字节数组，因为它提供了直接写入字符串的方法。

Note: The buffer size may be specified, or the default size may be used. A Writer sends its output immediately to the underlying character or byte stream.

让我们看看使用的构造函数 后来坚持使用此类的常规方法

构造函数： FileWriter（文件文件，布尔附加）：

它构造一个 FileWriter 对象，给定一个附加模式的 File 对象。现在让我们切换到此处调用的此类的方法，并在将字符串附加到现有文件中发挥关键作用，如下所示：

方法一： write()

此方法写入 String 的一部分

句法：

void write(String s,int off,int len);

返回类型：无效 

参数：

• 输入字符串
• 关闭
• 字符串长度

方法2：关闭（）

此方法在刷新后关闭流。

返回类型：无效

例子

Java

// Java Program to Append a String to the
// End of a File
 
// Importing input output classes
import java.io.*;
 
// Main class
class GeeksforGeeks {
 
    // Method 1
    // TO append string into a file
    public static void appendStrToFile(String fileName,
                                       String str)
    {
        // Try block to check for exceptions
        try {
 
            // Open given file in append mode by creating an
            // object of BufferedWriter class
            BufferedWriter out = new BufferedWriter(
                new FileWriter(fileName, true));
 
            // Writing on output stream
            out.write(str);
            // Closing the connection
            out.close();
        }
 
        // Catch block to handle the exceptions
        catch (IOException e) {
 
            // Display message when exception occurs
            System.out.println("exception occurred" + e);
        }
    }
 
    // Method 2
    // main driver method
    public static void main(String[] args) throws Exception
    {
        // Creating a sample file with some random text
        String fileName = "Geek.txt";
 
        // Try block to check for exceptions
        try {
 
            // Again operating same operations by passing
            // file as
            // parameter to read it
            BufferedWriter out = new BufferedWriter(
                new FileWriter(fileName));
 
            // Writing on. file
            out.write("Hello World:\n");
 
            // Closing file connections
            out.close();
        }
 
        // Catch block to handle exceptions
        catch (IOException e) {
 
            // Display message when error occurs
            System.out.println("Exception Occurred" + e);
        }
 
        // Now appendinggiven str to above
        // created file
        String str = "This is GeeksforGeeks";
 
        // Calling the above method
        appendStrToFile(fileName, str);
 
        // Let us print modified file
        try {
            BufferedReader in = new BufferedReader(
                new FileReader("Geek.txt"));
 
            String mystring;
 
            // TIll there is content in string
            // condition holds true
            while ((mystring = in.readLine()) != null) {
                System.out.println(mystring);
            }
        }
 
        // Catch block to handle IO exceptions
        catch (IOException e) {
            System.out.println("Exception Occurred" + e);
        }
    }
}

输出：