How to read files in java

There are four ways to read files in Java: FileInputStream is used to read bytes in binary files. FileReader is used to read characters in text files. Scanner can automatically resolve data types. NIO Files provides a modern file handling API.

How to read files using Java

To read files in Java, you can use the following methods:

1. The FileInputStream

FileInputStream class allows you to read bytes from a binary file. To use it, perform the following steps:

• Create a FileInputStream object, passing in the file path as a parameter.
• Use the read() method to read data. This method returns a byte representing the next byte.
• Repeatedly call the read() method until -1 is returned, indicating the end of the file.

2. FileReader

The FileReader class allows you to read characters from a text file. To use it, perform the following steps:

• Create a FileReader object, passing in the file path as argument.
• Use the read() method to read data. This method returns a character representing the next character.
• Repeatedly call the read() method until -1 is returned, indicating the end of the file.

3. Scanner

The Scanner class provides a more advanced method of reading files. It can automatically parse data types such as integers, floats, and strings. To use it, perform the following steps:

• Create a Scanner object, passing in a file path or an InputStream object as a parameter.
• Use the hasNext() method to check if there is more data.
• Use the next() method to read the next data item.

4.NIO Files

Java 7 introduced NIO Files, which provides a more modern file handling API. You can use the Files.readAllLines() method to read all lines in a file:

List<String> lines = Files.readAllLines(Paths.get("path/to/file.txt"));

Example:

The following is to read a text file Java program that prints content:

import java.io.File;
import java.io.FileReader;

public class ReadFile {
    public static void main(String[] args) {
        try {
            // 创建 FileReader 对象
            FileReader reader = new FileReader(new File("path/to/file.txt"));
            
            // 循环读取文件中的字符
            int ch;
            while ((ch = reader.read()) != -1) {
                // 打印字符
                System.out.print((char) ch);
            }
            
            // 关闭 FileReader 对象
            reader.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

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