【Java】file操作-删除文件中某一行中符合某一规则的

一时失言乱红尘 2022-09-16 04:52 155阅读 0赞

# 效果 #

此处规则，删除已空格分隔的域名行，为防止因制表符等引起误删，强制插入的规则空格分隔 
    同时要过滤掉# 和其他非自己插入的数据格式，避免误删

![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA55GeIOaWsA_size_20_color_FFFFFF_t_70_g_se_x_16]

# 代码 #

package com.ths.arsenaldnsnginxconfig.test;
    
    import java.io.BufferedReader;
    
    import java.io.FileReader;
    
    import java.io.File;
    
    import java.io.FileWriter;
    
    import java.io.FileNotFoundException;
    
    import java.io.IOException;
    
    import java.io.PrintWriter;
    import java.util.StringTokenizer;
    
    public class FileUtil { 
        public void removeLineFromFile(String file, String lineToRemove) { 
            try { 
                File inFile = new File(file);
                if (!inFile.isFile()) { 
                    System.out.println("Parameter is not an existing file");
                    return;
                }
    
    //Construct the new file that will later be renamed to the original filename.
                File tempFile = new File(inFile.getAbsolutePath() + ".tmp");
                BufferedReader br = new BufferedReader(new FileReader(file));
                PrintWriter pw = new PrintWriter(new FileWriter(tempFile));
    
                String line = null;
    
    //Read from the original file and write to the new
    
    //unless content matches data to be removed.
    // 考虑注解行 跳过 ，正常行 空格长度不一致正则尝试
                while ((line = br.readLine()) != null) { 
                    if (!findRealmName(line, lineToRemove)) { 
                        pw.println(line);
                        pw.flush();
                    }
                }
    
                pw.close();
                br.close();
    
    //Delete the original file
                if (!inFile.delete()) { 
                    System.out.println("Could not delete file");
                    return;
                }
    
    //Rename the new file to the filename the original file had.
                if (!tempFile.renameTo(inFile))
                    System.out.println("Could not rename file");
    
            } catch (FileNotFoundException ex) { 
                ex.printStackTrace();
            } catch (IOException ex) { 
                ex.printStackTrace();
    
            }
    
        }
    
        /**
         * 查找完全匹配的域名
         */
        private boolean findRealmName(String line, String s){ 
            System.out.println("当前行情况"+line);
            if (line.contains("\t")) { 
                System.out.println("当前行有制表符");
            }
            if (line.contains("#") || line.trim().isEmpty() || !line.contains(" ") || line.contains("\t"))
                return false;
            String[] sArr = line.trim().replaceAll(" +", " ").split(" ");
            System.out.println("切割到的空格后字符串"+ sArr[1]);
            String realmName = sArr[1].substring(0, sArr[1].lastIndexOf('.'));
            System.out.println("匹配到的字符串" + realmName);
            if (s.equals(realmName))
                return true;
            return false;
        }
    
    
    
    
      /*  public static void main(String[] args) { 
            FileUtil util = new FileUtil();
    
            util.removeLineFromFile("D:/about/dns/test.txt", "hub.cn");
    
        }
    */
    
        public static void main(String[] args) { 
    //        考虑删除此类异常情况多空格，空格数量不定
            String str = " abc def ghi mnopq r s ";
    //        法1
    //        StringTokenizer pas = new StringTokenizer(str, " ");
    //        str = ""; //这里清空了str，但StringTokenizer对象中已经保留了原来字符串的内容。
    //
    //        while (pas.hasMoreTokens()) { 
    //            String s = pas.nextToken();
    //            str = str + s + " ";
    //        }
    //        System.out.println(str.trim());
    //        法2
            String s = str.trim().replaceAll(" +", " ");
            System.out.println(s);
        }
    }

[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA55GeIOaWsA_size_20_color_FFFFFF_t_70_g_se_x_16]: /images/20220828/f99522e75c134076bb00816ee7926b8e.png