In Java, we can use ByteArrayInputStream to convert a String to an InputStream. String str = "mkyong.com"; InputStream is = new ByteArrayInputStream(str.getBytes(StandardCharsets.UTF_8)); Table of contents 1. ByteArrayInputStream 2. Apache Commons IO – IOUtils 3. Download Source Code 4. References 1. ByteArrayInputStream This example uses ByteArrayInputStream to convert a String to an InputStream and saves it …
In Java old days, it lacks of method to determine the free disk space on a partition. But this is changed since JDK 1.6 released, a few new methods – getTotalSpace(), getUsableSpace() and getFreeSpace(), are bundled with java.io.File to retrieve the partition or disk space detail. Example package com.mkyong; import java.io.File; public class DiskSpaceDetail { …
A Java program to demonstrate the use of java.io.File setReadOnly() method to make a file read only. Since JDK 1.6, a new setWritable() method is provided to make a file to be writable again. Example package com.mkyong; import java.io.File; import java.io.IOException; public class FileReadAttribute { public static void main(String[] args) throws IOException { File file …
A Java program to demonstrate the use of java.io.File isHidden() to check if a file is hidden. package com.mkyong; import java.io.File; import java.io.IOException; public class FileHidden { public static void main(String[] args) throws IOException { File file = new File("c:/hidden-file.txt"); if(file.isHidden()){ System.out.println("This file is hidden"); }else{ System.out.println("This file is not hidden"); } } } Note …
This article shows how to convert a file into a hexadecimal (hex) representative format. for example, below is a text file. /path/to/text.txt ABCDEFG 12345678 !@#$%^&*() Testing only And we will convert the above file into the following hex format. 41 42 43 44 45 46 47 0D 0A 31 32 33 34 35 36 | …
In this tutorial, it shows the use of java.lang.Comparable and java.util.Comparator to sort a Java object based on its property value. 1. Sort an Array To sort an Array, use the Arrays.sort(). String[] fruits = new String[] {"Pineapple","Apple", "Orange", "Banana"}; Arrays.sort(fruits); int i=0; for(String temp: fruits){ System.out.println("fruits " + ++i + " : " + …
Java example to show the use of Arrays.sort() to sort an Array. The code should be self-explanatory. import java.util.Arrays; import java.util.Collections; public class ArraySorting{ public static void main(String args[]){ String[] unsortStringArray = new String[] {"c", "b", "a", "3", "2", "1"}; int[] unsortIntArray = new int[] {7,5,4,6,1,2,3}; System.out.println("Before sort"); System.out.println("— unsortStringArray —"); for(String temp: unsortStringArray){ System.out.println(temp); …
By default, the ArrayList’s elements are display according to the sequence it is put inside. Often times, you may need to sort the ArrayList to make it alphabetically order. In this example, it shows the use of Collections.sort(‘List’) to sort an ArrayList. import java.util.ArrayList; import java.util.Collections; import java.util.List; public class SortArrayList{ public static void main(String …
Few Java examples to sort a Map by its keys or values. Note If you are using Java 8, refer to this article – How to use Stream APIs to sort a Map 1. Sort by Key 1.1 Uses java.util.TreeMap, it will sort the Map by keys automatically. SortByKeyExample1.java package com.mkyong.test; import java.util.HashMap; import java.util.Map; …
Here’s a few ways to initialize an java.util.ArrayList, see the following full example: InitArrayList.java package com.mkyong.examples; import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class InitArrayList { public static void main(String[] args) { //1. Normal way List<String> list = new ArrayList<String>(); list.add("String A"); list.add("String B"); list.add("String C"); System.out.println("List 1……"); for (String temp : list) { System.out.println(temp); …
This article show few ways of loop Map in Java. 1. Using entrySet() 2. Using forEach (Java 8 and later) 3. Using stream() (Java 8 and later) 4. Using iterator() 5. Using keySet() and get() 6. References 1. Using `entrySet()` Before Java 8, this is the most common method to loop a Map in Java. …
In the Terminal, we can use `javac -version` to check the installed JDK version and `java -version` to check the installed JRE version.
In Java, we can use the Java 1.7 FileVisitor or Apache Commons IO FileUtils.copyDirectory to copy a directory, which includes its sub-directories and files. This article shows a few of the common ways to copy a directory in Java. FileVisitor (Java 7+) FileUtils.copyDirectory (Apache commons-io) Custom Copy using Java 7 NIO and Java 8 Stream. …
Here’s an example to check if a directory is empty. Example package com.mkyong.file; import java.io.File; public class CheckEmptyDirectoryExample { public static void main(String[] args) { File file = new File("C:\\folder"); if(file.isDirectory()){ if(file.list().length>0){ System.out.println("Directory is not empty!"); }else{ System.out.println("Directory is empty!"); } }else{ System.out.println("This is not a directory"); } } }
If we use the NIO Files.delete to delete a non-empty directory in Java, it throws DirectoryNotEmptyException; for legacy IO File.delete to delete a non-empty directory, it returns a false. The standard solution is to loop the directory recursively, and delete all its children’s contents first (sub-files or sub-directories), and delete the parent later. This example …
In Java, we can use the NIO Files.createDirectory to create a directory or Files.createDirectories to create a directory including all nonexistent parent directories. try { Path path = Paths.get("/home/mkyong/a/b/c/"); //java.nio.file.Files; Files.createDirectories(path); System.out.println("Directory is created!"); } catch (IOException e) { System.err.println("Failed to create directory!" + e.getMessage()); } 1. Create Directory – Java NIO 1.1 We can …
This article shows how to move a file to another directory in the same file drive or remote server. Files.move – Move file in local system. JSch – Move file to remove server (SFTP) 1. Move file to another directory This Java example uses NIO Files.move to move a file from to another directory in …
In Java, we can use the following two Files.createTempFile() methods to create a temporary file in the default temporary-file directory. Path createTempFile(Path dir, String prefix, String suffix, FileAttribute<?>… attrs) throws IOException Path createTempFile(String prefix, String suffix, FileAttribute<?>… attrs) throws IOException The default temporary file folder is vary on operating system. Windows – %USER%\AppData\Local\Temp Linux – …
In Java, we can use the NIO Files.setLastModifiedTime(path, FileTime) to update the last modified date or time of a file. Path path = Paths.get("/path/file"); LocalDate newLocalDate = LocalDate.of(1997, 12, 31); // year, month, dayOfMonth, hour, minute, second LocalDateTime newLocalDateTime = LocalDateTime.of(1999, 9, 30, 10, 30, 22); // convert LocalDateTime to Instant Instant instant = newLocalDateTime.toInstant(ZoneOffset.UTC); …
This article shows how to use the following Java APIs to append text to the end of a file. Files.write – Append a single line to a file, Java 7. Files.write – Append multiple lines to a file, Java 7, Java 8. Files.writeString – Java 11. FileWriter FileOutputStream FileUtils – Apache Commons IO. In Java, …
In Java (@since 1.7), we can use the NIO Files.readAttributes to get all the file metadata, including the file creation date. Path file = Paths.get(fileName); BasicFileAttributes attr = Files.readAttributes(file, BasicFileAttributes.class); System.out.println("creationTime: " + attr.creationTime()); // creationTime: 2020-07-20T09:29:54.627222Z 1. Files.readAttributes (NIO) This example uses Files.readAttributes to print the file creation date. GetCreationDate1.java package com.mkyong.io.howto; import java.io.IOException; …
This article shows four ways to copy a file in Java. Files.copy (NIO) Apache Commons IO Guava Plain Java In Java 7+, the NIO Files.copy is the simplest way to copy a file, because it is a built-in API. Before Java 7, the Apache Commons IO FileUtils.copyFile is a preferable solution because the legacy IO …
In Java, we can use the NIO Files.delete() or Files.deleteIfExists() to delete a temporary file, it works the same like delete a regular text file. // create a temporary file Path path = Files.createTempFile(null, ".log"); // delete Files.delete(path); // or if(Files.deleteIfExists(path)){ // success }else{ // file does not exist } 1. Delete Temporary File – …
In Java, we can use the NIO Files.delete(Path) and Files.deleteIfExists(Path) to delete a file. 1. Delete a file with Java NIO 1.1 The Files.delete(Path) deletes a file, returns nothing, or throws an exception if it fails. DeleteFile1.java package com.mkyong.io.file; import java.io.IOException; import java.nio.file.Files; import java.nio.file.Paths; public class DeleteFile1 { public static void main(String[] args) { …
In Java, we can use the NIO Files.move(source, target) to rename or move a file. import java.io.IOException; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; //… Path source = Paths.get("/home/mkyong/newfolder/test1.txt"); Path target = Paths.get("/home/mkyong/newfolder/test2.txt"); try{ Files.move(source, target); } catch (IOException e) { e.printStackTrace(); } 1. Rename a file in the same directory. 1.1 This example renames a …
In Java, we can use BufferedWriter to write content into a file. // jdk 7 try (FileWriter writer = new FileWriter("app.log"); BufferedWriter bw = new BufferedWriter(writer)) { bw.write(content); } catch (IOException e) { System.err.format("IOException: %s%n", e); } Note If possible, uses Files.write instead, one line, simple and nice. List<String> list = Arrays.asList("Line 1", "Line 2"); …
The temporary file is just a regular file created on a predefined directory. In Java, we can use the NIO Files.write() to write data to a temporary file. // create a temporary file Path tempFile = Files.createTempFile(null, null); // Writes a string to the above temporary file Files.write(tempFile, "Hello World\n".getBytes(StandardCharsets.UTF_8)); // Append List<String> content = …
In Java, for NIO Path, we can use path.toAbsolutePath() to get the file path; For legacy IO File, we can use file.getAbsolutePath() to get the file path. For symbolic links or file path contains . or .., we can use path.toRealPath() or file.getCanonicalPath() to get the real file pah. Below is the mapping of File …
This article shows few Java examples to get the total number of lines in a file. The steps are similar: Open the file. Read line by line, and increases count + 1 each line. Close the file. Read the count. Test Java Methods: Files.lines BufferedReader LineNumberReader BufferedInputStream At the end of the article, we also …
In this tutorial, we will show you three Java examples to construct a file path : File.separator or System.getProperty(“file.separator”) (Recommended) File file = new File(workingDir, filename); (Recommended) Create the file separator manually. (Not recommend, just for fun) 1. File.separator Classic Java example to construct a file path, using File.separator or System.getProperty(“file.separator”). Both will check the …
In Java, we can use Files.size(path) to get the size of a file in bytes. // size in bytes long bytes = Files.size(path); 1. Files.size (NIO) This example uses NIO Files.size(path) to print the size of an image file (140 kb). GetFileSize.java package com.mkyong.io.howto; import java.io.IOException; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; public class GetFileSize …
In Java, we can use System.getProperty("java.io.tmpdir") to get the default temporary file location. For Windows, the default temporary folder is %USER%\AppData\Local\Temp For Linux, the default temporary folder is /tmp 1. java.io.tmpdir Run the below Java program on a Ubuntu Linux. TempFilePath1 package com.mkyong.io.temp; public class TempFilePath1 { public static void main(String[] args) { String tmpdir …
We can use DecimalFormat(“0.00”) or BigDecimal to round float / double to 2 decimal places.
In Java, FileOutputStream is a bytes stream class that’s used to handle raw binary data. To write the data to file, you have to convert the data into bytes and save it to file. See below full example. package com.mkyong.io; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; public class WriteFileExample { public static void main(String[] args) …
In Java, file permissions are very OS specific: *nix , NTFS (windows) and FAT/FAT32, all have different kind of file permissions. Java comes with some generic file permission to deal with it. Check if the file permission allow : file.canExecute(); – return true, file is executable; false is not. file.canWrite(); – return true, file is …
In Java, there are many ways to create and write to a file. Files.newBufferedWriter (Java 8) Files.write (Java 7) PrintWriter File.createNewFile Note I prefer the Java 7 nio Files.write to create and write to a file, because it has much cleaner code and auto close the opened resources. Files.write( Paths.get(fileName), data.getBytes(StandardCharsets.UTF_8)); 1. Java 8 Files.newBufferedWriter …
A very important question in mathematics and security is telling whether a number is prime or not. This is pretty useful when encrypting a password. In this tutorial, you will learn how to find whether a number is prime in simple cases. Trivial Cases We learned numbers are prime if the only divisors they have …
This article shows a few ways to save a byte[] into a file. For JDK 1.7 and above, the NIO Files.write is the simplest solution to save byte[] to a file. // bytes = byte[] Path path = Paths.get("/path/file"); Files.write(path, bytes); FileOutputStream is the best alternative. try (FileOutputStream fos = new FileOutputStream("/path/file")) { fos.write(bytes); //fos.close …
In Java, we can use Files.readAllBytes(path) to convert a File object into a byte[]. import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; String filePath = "/path/to/file"; // file to byte[], Path byte[] bytes = Files.readAllBytes(Paths.get(filePath)); // file to byte[], File -> Path File file = new File(filePath); byte[] bytes = Files.readAllBytes(file.toPath()); P.S The NIO Files class is …
Quartz is a powerful and advance scheduler framework, to help Java developer to scheduler a job to run at a specified date and time. This tutorial show you how to develop a scheduler job using Quartz 1.6.3. Note This example is a bit outdate, unless you are still using the old Quartz 1.6.3 library, otherwise, …