Filehand

File

By Arasaka Teacher

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String name = "abc.txt";
File file = new File(name);
System.out.println(file.exists());
try {
// 使用 FileReader 打开文件
使用 BufferedReader 包装 FileReader，提高读取效率
// 用于存储从文件中读取的每一行内容
String line;
// 先读取一行

//条件是什么

{
// 输出当前行
System.out.println(line);
// 读取下一行
line = reader.readLine();
}
} ; // 处理异常
}

• FileReader fileReader = new FileReader(file);

• BufferedReader reader = new BufferedReader(fileReader);

• line = reader.readLine();

• while (line != null)

• catch (IOException e) {
  e.printStackTrace()

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Drag and Drop

// 1. 使用 File 类创建文件对象

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// 4. 将内容写入文件

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// 写入多行内容





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;

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File file = new File(name);

FileWriter fileWriter = new FileWriter(file);

fileWriter.write(content);

File file = new File();

FileWriter fileWriter = new FileWriter();

fileWriter.append(content);

fileWriter.close()

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Before performing any file operations, the file must be

in a specified mode.

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import java.io.*;

public class ReadData {

public static void main(String[] args) {

String name = "abc.txt"; // 文件名

String line;

try (BufferedReader reader = new BufferedReader(new FileReader(name))) {

int i = 0;

// 在此处填入合适的代码，使循环能读取文件前 10 行

while (

) {

// 读取文件中的每一行

line = reader.readLine();

// 打印出当前行内容

System.out.println(line);

i++; // 计数器增加

}

} catch (IOException e) {

e.printStackTrace(); // 捕获并打印异常

}

}

}

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import java.io.*;

public class ReadAndCount {

public static void main(String[] args) {

String fileName = "test.txt";

String line;

int lineCount = 0;

int nonEmptyLineCount = 0;

try (BufferedReader reader = new BufferedReader(new FileReader(fileName))) {

while(lineCount < 5) && ((line = reader.readLine()) != null) {

line = reader.readLine();

if (line != null && !line.trim().isEmpty()) {

————————++

}

——————++;

}

System.out.println("非空行数量: " + nonEmptyLineCount);

} catch (IOException e) {

e.printStackTrace();

}

}

}

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The command to open a file for reading is written as:

<file identifier> FOR READ.

Answer:

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To add data to an existing file without overwriting its contents, the file should be opened in

mode.

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• The command used to read the next line of text from a file is

  <file identifier>, <variable>.

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The function

is used to check whether there are any more lines to be read from a file.

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To close a file after it is no longer needed, use the

command.

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Data is written into the file (after the file has been opened in WRITE or APPEND mode) using the

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Write several lines of text to the file.

DECLARE textLn : STRING

DECLARE myFile : STRING

myFile ← "myText.txt"

REPEAT

    OUTPUT "Please enter a line of text"

  

IF textLn <> ""

    THEN

       

    ELSE

      

    ENDIF

OUTPUT "The file contains these lines of text:"

• OPEN myFile FOR WRITE

•   INPUT textLn

•  WRITEFILE myFile, textLn

•   CLOSEFILE(myFile)

• UNTIL textLn = ""

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This example uses the operations together, to copy all the lines from FileA.txt to FileB.txt,

replacing any blank lines by a line of dashes.

DECLARE LineOfText : STRING

• OPENFILE "FileA.txt" FOR READ

  OPENFILE "FileB.txt" FOR WRITE

• WHILE NOT EOF("FileA.txt")

  READFILE "FileA.txt", LineOfText

• IF LineOfText = "" THEN

  WRITEFILE "FileB.txt", " ----------------------------"

• ELSE

  WRITEFILE "FileB.txt", LineOfText

• ENDIF

  ENDWHILE

  CLOSEFILE "FileA.txt"

  CLOSEFILE "FileB.txt"

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Create a text file.

DECLARE myTextFile : STRING

← "myText.txt"

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OUTPUT "The file contains these lines of text:"

REPEAT

• OPEN myTextFile FOR READ

•     READFILE, textIn

•     OUTPUT textIn

• UNTIL EOF(myTextFile)

• CLOSEFILE(myTextFile)

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Append a line of text at the end of the file.

DECLARE textIn : STRING

REPEAT

   

       

    ELSE

   

• OPEN myTextFile FOR APPEND

•     OUTPUT "Please enter a line of text"

      INPUT textIn

•  IF textIn <> "" THEN

•  WRITEFILE, textIn

•      CLOSEFILE(myTextFile)

      ENDIF

  UNTIL textIn = ""

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