Java文件 (Java files)
The file is a class of java.io package.
該文件是java.io包的類。
If we create a file then we need to remember one thing before creating a file. First, we need to check whether a file exists of the same name or not. If a file of the same name exists then we can’t create a file of same name else we can create a file of same.
如果創建文件，那么在創建文件之前我們需要記住一件事。 首先，我們需要檢查文件是否存在相同名稱。 如果存在同名文件，那么我們將無法創建同名文件，否則我們將創建同名文件。
We will study three things:
我們將研究三件事：
Creating a file
建立檔案
Reading a file
讀取文件
Writing a file
寫文件
1) Creating a file
1)創建一個文件
To create a file by using createNewFile() method and the return type of this method is Boolean so it returns true or false. It returns true during successful creation of the file and It returns false during the creation of file failure.
要使用createNewFile()方法創建文件，并且此方法的返回類型為Boolean，因此它將返回true或false。 成功創建文件時返回true，創建文件失敗時返回false。
Example:
例：
// import the File class because we will use File class methods
import java.io.File;
//import the Exception class because it may raise
//an exception when working with files
import java.lang.Exception;
public class CreateFile {
public static void main(String[] args) {
try {
// Specify the path of file and we use double slashes
// to escape '\' character sequence for windows otherwise
// it will be considerable as url.
File file = new File("C:\\Users\\computer clinic\\OneDrive\\Articles\\myjava.txt");
// createNewFile() returns true if file is successfully
// created and then we will get the name of the file
// using getName() method and return false if the file
// is already exists then we will get the message
if (file.createNewFile()) {
System.out.println("File created: " + file.getName());
} else {
System.out.println("File already exists of same name!! Please try to create from other name ");
}
} catch (Exception e) {
System.out.println("An error occurred.");
e.printStackTrace();
}
}
}
Output
輸出量
D:\Programs>javac CreateFile.java
D:\Programs>java
File created: myjava.txt
2) Writing a file
2)寫文件
To write a file by using write() method of FileWriter class.
使用FileWriter類的write()方法寫入文件。
Example:
例：
// import the FileWriter class because
// we will use FileWriter class methods write()
import java.io.FileWriter;
//import the Exception class because it may raise
// an exception when working with files
import java.lang.Exception;
public class WriteFile {
public static void main(String[] args) {
try {
// Create an object of FileWriter class
FileWriter fw = new FileWriter("C:\\Users\\computer clinic\\OneDrive\\Articles\\myjava.txt ");
// To write a file by using write() method
fw.write("We are going to write a file by using write()");
// After writing a file then we need to close safely
fw.close();
//After successfully written of file then display a message for the user
System.out.println("File has been written successfully");
} catch (Exception e) {
System.out.println("An error occurred");
e.printStackTrace();
}
}
}
Output
輸出量
D:\Programs>javac WriteFile.java
D:\Programs>java WriteFile
File has been written successfully
3) Reading a file
3)讀取文件
To read a file by using nextLine() method of Scanner class.
通過使用Scanner類的nextLine()方法讀取文件。
Example:
例：
// import the File class because we will
// use File class methods
import java.io.File;
//import the Exception class because it may
// raise an exception when working with files
import java.lang.Exception;
// import the Scanner class to read file from user
import java.util.Scanner;
public class ReadFile {
public static void main(String[] args) {
try {
File fr = new File("C:\\Users\\computer clinic\\OneDrive\\Articles\\myjava.txt ");
Scanner sc = new Scanner(fr);
while (sc.hasNextLine()) {
String file_read = sc.nextLine();
System.out.println(file_read);
}
sc.close();
} catch (Exception e) {
System.out.println("An error occurred.");
e.printStackTrace();
}
}
}
Output
輸出量
D:\Programs>javac ReadFile.java
D:\Programs>java ReadFile
We are going to write a file by using write()
翻譯自: https://www.includehelp.com/java/what-are-java-files.aspx
