This article shares the specific code of Java file reading and writing tool for your reference. The specific content is as follows
import java.io.BufferedInputStream;import java.io.BufferedOutputStream;import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.FileReader;import java.io.FileReader;import java.io.FileWriter;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.io.PrintWriter;import java.net.URLEncoder;import java.util.ArrayList;import java.util.Calendar;import java.util.Date;import java.util.HashMap;import java.util.HashSet;import java.util.List;import javax.servlet.http.HttpServletResponse;/** * <p>File operation tool class<p> * @version 1.0 * @author li_hao * @date January 18, 2017 */@SuppressWarnings({"resource","unused"})public class FileUtils { /** * Get the project root directory of windows/linux* @return */ public static String getConTextPath(){ String fileUrl = Thread.currentThread().getContextClassLoader().getResource("").getPath(); if("usr".equals(fileUrl.substring(1,4))){ fileUrl = (fileUrl.substring(0,fileUrl.length()-16));//linux }else{ fileUrl = (fileUrl.substring(1,fileUrl.length()-16));//windows } return fileUrl; } /** * String to array* @param str String* @param splitStr delimiter* @return */ public static String[] StringToArray(String str,String splitStr){ String[] arrayStr = null; if(!"".equals(str) && str != null){ if(str.indexOf(splitStr)!=-1){ arrayStr = str.split(splitStr); }else{ arrayStr = new String[1]; arrayStr[0] = str; } } return arrayStr; } /** * Read file* * @param Path * @return */ public static String ReadFile(String Path) { BufferedReader reader = null; String laststr = ""; try { FileInputStream fileInputStream = new FileInputStream(Path); InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, "UTF-8"); reader = new BufferedReader(inputStreamReader); String tempString = null; while ((tempString = reader.readLine()) != null) { laststr += tempString; } reader.close(); } catch (IOException e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } } return laststr; } /** * Get the names of all files in the folder + fuzzy query (when there is no need for fuzzy query, queryStr can be passed empty or null) * 1. When the path does not exist, map returns the retType value is 1 * 2. When the path is a file path, map returns the retType value is 2, filename fileName value is filename* 3. When there is a folder under the path, map returns the retType value is 3, filename list fileNameList, foldername list folderNameList * @param folderPath Path * @param queryStr fuzzy query string * @return */ public static HashMap<String, Object> getFilesName(String folderPath , String queryStr) { HashMap<String, Object> map = new HashMap<>(); List<String> fileNameList = new ArrayList<>();//File name list List<String> folderNameList = new ArrayList<>();//Folder name list File f = new File(folderPath); if (!f.exists()) { //The path does not exist map.put("retType", "1"); }else{ boolean flag = f.isDirectory(); if(flag==false){ //The path is file map.put("retType", "2"); map.put("fileName", f.getName()); }else{ //The path is folder map.put("retType", "3"); File fa[] = f.listFiles(); queryStr = queryStr==null ? "" : queryStr;//If queryStr is passed to null, replace it with empty (indexOf matching value cannot be null) for (int i = 0; i < fa.length; i++) { File fs = fa[i]; if(fs.getName().indexOf(queryStr)!=-1){ if (fs.isDirectory()) { folderNameList.add(fs.getName()); } else { fileNameList.add(fs.getName()); } } } map.put("fileNameList", fileNameList); map.put("folderNameList", folderNameList); } } return map; } /** * Read the file in units of behavior and read to the last line* @param filePath * @return */ public static List<String> readFileContent(String filePath) { BufferedReader reader = null; List<String> listContent = new ArrayList<>(); try { reader = new BufferedReader(new FileReader(filePath)); String tempString = null; int line = 1; // Read one line at a time until null is the end of the file while ((tempString = reader.readLine()) != null) { listContent.add(tempString); line++; } reader.close(); } catch (IOException e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e1) { } } } return listContent; } /** * Read the specified row data, note: 0 is the start line* @param filePath * @param lineNumber * @return */ public static String readLineContent(String filePath,int lineNumber) { BufferedReader reader = null; String lineContent=""; try { reader = new BufferedReader(new FileReader(filePath)); int line=0; while(line<=lineNumber){ lineContent=reader.readLine(); line++; } reader.close(); } catch (IOException e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e1) { } } return lineContent; } /** * Read data from beginLine to endLine (including beginLine and endLine), note: 0 is the start line* @param filePath * @param beginLineNumber Start line* @param endLineNumber End line* @return */ public static List<String> readLinesContent(String filePath,int beginLineNumber,int endLineNumber){ List<String> listContent = new ArrayList<>(); try{ int count = 0; BufferedReader reader = new BufferedReader(new FileReader(filePath)); String content = reader.readLine(); while(content !=null){ if(count >= beginLineNumber && count <=endLineNumber){ listContent.add(content); } content = reader.readLine(); count++; } } catch(Exception e){ } return listContent; } /** * Read all data in several files* @param listFilePath * @return */ public static List<String> readFileContent_list(List<String> listFilePath) { List<String> listContent = new ArrayList<>(); for(String filePath : listFilePath){ File file = new File(filePath); BufferedReader reader = null; try { reader = new BufferedReader(new FileReader(file)); String tempString = null; int line = 1; // Read one line at a time until null is the end of the file while ((tempString = reader.readLine()) != null) { listContent.add(tempString); line++; } reader.close(); } catch (IOException e) { e.printStackTrace(); } finally { if (reader != null) { try { reader.close(); } catch (IOException e1) { } } } } return listContent; } /** * File data is written (if folders and files do not exist, they are created first and then written) * @param filePath * @param content * @param flag true: If the file exists and contents exist, the content is added in a new line; false: If the file exists and contents exists, the contents are replaced*/ public static String fileLinesWrite(String filePath,String content,boolean flag){ String filedo = "write"; FileWriter fw = null; try { File file=new File(filePath); //If the folder does not exist, create the folder if (!file.getParentFile().exists()){ file.getParentFile().mkdirs(); } if(!file.exists()){//If the file does not exist, create the file and write the first line of content file.createNewFile(); fw = new FileWriter(file); filedo = "create"; }else{//If the file exists, append or replace the content fw = new FileWriter(file, flag); } } catch (IOException e) { e.printStackTrace(); } PrintWriter pw = new PrintWriter(fw); pw.println(content); pw.flush(); try { fw.flush(); pw.close(); fw.close(); } catch (IOException e) { e.printStackTrace(); } return filedo; } /** * Write file* @param ins * @param out */ public static void writeIntoOut(InputStream ins, OutputStream out) { byte[] bb = new byte[10 * 1024]; try { int cnt = ins.read(bb); while (cnt > 0) { out.write(bb, 0, cnt); cnt = ins.read(bb); } } catch (IOException e) { e.printStackTrace(); } finally { try { out.flush(); ins.close(); out.close(); } catch (IOException e) { e.printStackTrace(); } } } /** * Determine whether the elements in the list are exactly the same (return true if exactly the same, otherwise return false) * @param list * @return */ private static boolean hasSame(List<? extends Object> list){ if(null == list) return false; return 1 == new HashSet<Object>(list).size(); } /** * Determine whether there are duplicate elements in the list (return true if no duplicate, otherwise return false) * @param list * @return */ private static boolean hasSame2(List<? extends Object> list){ if(null == list) return false; return list.size() == new HashSet<Object>(list).size(); } /** * Increase/decrease the number of days* @param date * @param num * @return */ public static Date DateAddOrSub(Date date, int num) { Calendar startDT = Calendar.getInstance(); startDT.setTime(date); startDT.add(Calendar.DAY_OF_MONTH, num); return startDT.getTime(); } }The above is all the content of this article. 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