Java Using Objects When Reading in File Data

Prior to Coffee 7, reading a text file into an ArrayList involves a lot of average coding, as you need to read the file line by line and insert each line into an ArrayList, but from Java 7 onward, y'all tin can use the utility method Files.readAllLines() to read all lines of a text file into a List. This method returns a List of String that contains all lines of files. Afterward yous can convert this List to ArrayList, LinkedList, or whatsoever listing you want to. Btw, this the fourth article in the serial of reading a text file in Java.

In the earlier parts, yous take learned how to read a file using Scanner and BufferedReader (ane). And so, reading the whole file as Cord (2) and finally reading a text file into an array (three ). This plan is not very different from those in terms of fundamentals.

We are still going to use theread() method for Java six solution and will read all text until this method returns -i which signals the end of the file.

Reading text file into ArrayList in Java - BufferedReader Case

If you lot know how to read a file line past line, either past using Scanner or past using BufferedReader so reading a text file into ArrayList is not hard for you. All you demand to do is read each line and store that into ArrayList, equally shown in the following example:

            BufferedReader bufReader            =            new            BufferedReader(new            FileReader("file.txt"));     ArrayList<String> listOfLines            =            new            ArrayList<>();            String            line            =            bufReader.readLine();            while            (line            !            =            goose egg) {       listOfLines.add(line);       line            =            bufReader.readLine();     }      bufReader.shut();

Just remember to close the BufferedReader once yous are done to prevent resources leak, as you lot don't have a try-with-resource statement in Coffee half dozen.

Reading text file into List in Java - Files.readAllLines Instance

In Java seven, you don't demand to write code to read and store into ArrayList, simply phone call the Files.readAllLines() method and this will return you a listing of String, where each element is the corresponding line from the line. Since List is an ordered drove the society of lines in a file is preserved in the listing. You can later convert this List to ArrayList or any other implementation.

here is sample code to read text file into List in JDK 7:

            public            static            List<String> readFileIntoList(String            file) {            Listing<String> lines            =            Collections.emptyList();            try            {       lines            =            Files.readAllLines(Paths.get(file), StandardCharsets.UTF_8);     }            catch            (IOException e) {            // TODO Auto-generated take hold of block            east.printStackTrace();     }            return            lines;   }

The readAllLines() method accepts a CharSet, yous can use a pre-divers character set due east.g. StandardCharsets.UTF_8 or StandardCharsets.UTF_16.  You can too see these free Java Courses to larn more about new file utility classes introduced in Coffee 7 and viii.

Java Programme to read text file into ArrayList

Here is the consummate Java program to demonstrate both methods to read a text file into ArrayList. This program offset teaches you lot how to exercise this in JDK vii or Coffee 8 using theFiles.readAllLines() method and later using BufferedReader and ArrayList in Java 6 and lower version.

You can compile and run this programme from the command prompt or if you want to run in Eclipse, just copy and paste in Eclipse Java project. The Eclipse IDE will automatically create a source file for you.

Then just right-click and Run equally Java Program. Make sure you take file.txt in your classpath. Since I have given the relative path here, brand sure you put that file within the Eclipse project directory.

Reading text file into ArrayList in Java

            import            java.io.BufferedReader;            import            java.io.FileReader;            import            coffee.io.IOException;            import            java.nio.charset.StandardCharsets;            import            coffee.nio.file.Files;            import            java.nio.file.Paths;            import            java.util.ArrayList;            import            java.util.Collections;            import            java.util.List;            /*  * Java Program read a text file into ArrayList in Java 6  * and Coffee eight.   */            public            class            ReadFileIntoArrayList            {            public            static            void            principal(String[] args) throws Exception {            // reading text file into List in Java 7            List<Cord> lines            =            Collections.emptyList();            try            {       lines            =            Files.readAllLines(Paths.get("file.txt"), StandardCharsets.UTF_8);     }            catch            (IOException e) {            // TODO Auto-generated grab block            e.printStackTrace();     }            Organization.out.println("Content of List:");            System.out.println(lines);            // reading text file into ArrayList in Java half-dozen            BufferedReader bufReader            =            new            BufferedReader(new            FileReader("file.txt"));     ArrayList<String> listOfLines            =            new            ArrayList<>();            String            line            =            bufReader.readLine();            while            (line            !            =            zero) {       listOfLines.add(line);       line            =            bufReader.readLine();     }      bufReader.close();            System.out.println("Content of ArrayLiList:");            System.out.println(listOfLines);    }  }   Output Content of            List            :            [Python, Cherry, JavaScript] Content of ArrayLiList:            [Python, Scarlet, JavaScript]

That's all about how to read a text file into ArrayList in Java. You lot can see information technology's very easy in Java 7 and Coffee 8 by using Files.readAllLines() method. Though you should be mindful of character encoding while reading a text file in Java.

 In Coffee vi besides, the solution using BufferedReader or Scanner is not very hard to implement, but the thing you need to remember is that yous are loading the whole file into retentiveness.

If the file is likewise large and you don't accept enough memory, your program will dice by throwing java.lang.OutOfMemoryError: Java Heap Space. In short, this solution is simply adept for a small files, for the large files yous should always read past streaming.

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Source: https://www.java67.com/2016/07/how-to-read-text-file-into-arraylist-in-java.html

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