删除文本文件中重复行的 Java 程序
原文:https://www . geesforgeks . org/Java-program-delete-replica-line-text-file/
给定一个文件 input.txt。我们的任务是删除其中的重复行,并将输出保存在文件中,比如 output.txt
朴素算法:
1\. Create PrintWriter object for output.txt
2\. Open BufferedReader for input.txt
3\. Run a loop for each line of input.txt
3.1 flag = false
3.2 Open BufferedReader for output.txt
3.3 Run a loop for each line of output.txt
-> If line of output.txt is equal to current line of input.txt
-> flag = true
-> break loop
4\. Check flag, if false
-> write current line of input.txt to output.txt
-> Flush PrintWriter stream
5\. Close resources.
要成功运行以下程序,input.txt 必须存在于同一个文件夹中,或者为其提供完整路径。
// Java program to remove
// duplicates from input.txt and
// save output to output.txt
import java.io.*;
public class FileOperation
{
public static void main(String[] args) throws IOException
{
// PrintWriter object for output.txt
PrintWriter pw = new PrintWriter("output.txt");
// BufferedReader object for input.txt
BufferedReader br1 = new BufferedReader(new FileReader("input.txt"));
String line1 = br1.readLine();
// loop for each line of input.txt
while(line1 != null)
{
boolean flag = false;
// BufferedReader object for output.txt
BufferedReader br2 = new BufferedReader(new FileReader("output.txt"));
String line2 = br2.readLine();
// loop for each line of output.txt
while(line2 != null)
{
if(line1.equals(line2))
{
flag = true;
break;
}
line2 = br2.readLine();
}
// if flag = false
// write line of input.txt to output.txt
if(!flag){
pw.println(line1);
// flushing is important here
pw.flush();
}
line1 = br1.readLine();
}
// closing resources
br1.close();
pw.close();
System.out.println("File operation performed successfully");
}
}
输出:
File operation performed successfully
注意:如果在 cwd(当前工作目录)中存在 output.txt,那么它将被上述程序覆盖,否则将创建新文件。
一个更好的解决方案是使用 HashSet 来存储 input.txt 的每一行,由于 Set 会忽略重复的值,所以在存储一行时,检查它是否已经存在于 HashSet 中。仅当 hashset 中不存在时,才将其写入 output.txt。
要成功运行以下程序,input.txt 必须存在于同一文件夹中,或者为它们提供完整路径。
// Efficient Java program to remove
// duplicates from input.txt and
// save output to output.txt
import java.io.*;
import java.util.HashSet;
public class FileOperation
{
public static void main(String[] args) throws IOException
{
// PrintWriter object for output.txt
PrintWriter pw = new PrintWriter("output.txt");
// BufferedReader object for input.txt
BufferedReader br = new BufferedReader(new FileReader("input.txt"));
String line = br.readLine();
// set store unique values
HashSet<String> hs = new HashSet<String>();
// loop for each line of input.txt
while(line != null)
{
// write only if not
// present in hashset
if(hs.add(line))
pw.println(line);
line = br.readLine();
}
pw.flush();
// closing resources
br.close();
pw.close();
System.out.println("File operation performed successfully");
}
}
输出:
File operation performed successfully
注意:如果在 cwd(当前工作目录)中存在 output.txt,那么它将被上述程序覆盖,否则将创建新文件。
本文由高拉夫·米格拉尼供稿。如果你喜欢 GeeksforGeeks 并想投稿,你也可以使用contribute.geeksforgeeks.org写一篇文章或者把你的文章邮寄到 contribute@geeksforgeeks.org。看到你的文章出现在极客博客主页上,帮助其他极客。
如果你发现任何不正确的地方,或者你想分享更多关于上面讨论的话题的信息,请写评论。
版权属于:月萌API www.moonapi.com,转载请注明出处