Java uses the read() function of the InputStream class to read the file content

Java uses the read() function of the InputStream class to read the file content

In Java programming, we often need to read content from files. Java provides various classes and methods for file operations, among which the InputStream class is one of the basic classes for reading bytes from an input stream. This article will introduce how to use the read() function of the InputStream class to read the contents of a file, and comes with code examples.

The InputStream class is an abstract class in the Java IO library. It is the super class of all input stream classes. We can use subclasses of the InputStream class to read data from various input sources such as files, network connections, processes, etc. The read() function of the InputStream class is a method used to read the next byte in the input stream, and the return value is of type int.

The following is a simple code example that demonstrates how to read the file content using the read() function of the InputStream class:

import java.io.FileInputStream;
import java.io.InputStream;

public class ReadFileExample {
    public static void main(String[] args) {
        try {
            // 创建一个文件输入流
            InputStream input = new FileInputStream("example.txt");

            // 定义一个字节数组，用于存储读取到的数据
            byte[] buffer = new byte[1024];

            // 定义一个变量，用于记录每次读取到的字节数
            int bytesRead;

            // 循环读取文件内容
            while ((bytesRead = input.read(buffer)) != -1) {
                // 将读取到的内容转换为字符串并打印出来
                String content = new String(buffer, 0, bytesRead);
                System.out.println(content);
            }

            // 关闭输入流
            input.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

In the above code example, we first create a file input Stream, specify the file to be read as "example.txt". Then we define a byte array buffer to store the data read each time. Next, we use a while loop to continuously call the input.read(buffer) function to read the file content until the end of the file. The number of bytes read each time is stored in the bytesRead variable. We use this variable to limit the length of the string to avoid printing invalid data. Finally, we close the input stream and release system resources.

With the above code example, we can easily read the contents of the file. It should be noted that in actual development, we should check whether the file exists, whether it is readable and other abnormal conditions before reading the file content. In the code, we use try-catch blocks to catch possible exceptions and print exception information.

Summary:

This article introduces how to use the read() function of Java's InputStream class to read file contents. Through this function, we can read the file content byte by byte and convert the bytes into strings for processing. It should be noted that when reading the file content, we should use a loop to ensure that the end of the file is read, and at the same time close the input stream in time to release system resources. I hope this article can help you learn and understand Java file operations.

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