Java Reading a file into an array

Question

I have a file  called  number txt   which I want to read to an array in Java  How exactly do I go ahead and do this  It is a straight-forward  1-dimensional  file  containing 100 numbers   The problem is that I get an exception every time  Apparently it can t find it  I am sure its spelled correctly   When looking through code examples  it doesn t specify the file s entire file path  only the name of the file itself  How would I go about doing that if its necessary   Also  when reading the file  will the array automatically contain all the lines of the file  or will I have to make a loop which which copies every line to corresponding subscript i   I ve heard of BufferedReader class  what it s purpose  and how does it corelate to reading input

User · Answer

Here is some example code to help you get started:

package com.acme;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class FileArrayProvider {

    public String[] readLines(String filename) throws IOException {
        FileReader fileReader = new FileReader(filename);
        BufferedReader bufferedReader = new BufferedReader(fileReader);
        List<String> lines = new ArrayList<String>();
        String line = null;
        while ((line = bufferedReader.readLine()) != null) {
            lines.add(line);
        }
        bufferedReader.close();
        return lines.toArray(new String[lines.size()]);
    }
}

And an example unit test:

package com.acme;

import java.io.IOException;

import org.junit.Test;

public class FileArrayProviderTest {

    @Test
    public void testFileArrayProvider() throws IOException {
        FileArrayProvider fap = new FileArrayProvider();
        String[] lines = fap
                .readLines("src/main/java/com/acme/FileArrayProvider.java");
        for (String line : lines) {
            System.out.println(line);
        }
    }
}

Hope this helps.

User · Answer

Apache Commons I O provides FileUtils readLines    which should be fine for all but huge files  http   commons apache org io api-release index html  The 2 1 distribution includes FileUtils lineIterator    which would be suitable for large files  Google s Guava libraries include similar utilities

User · Answer

You should be able to use forward slashes in Java to refer to file locations   The BufferedReader class is used for wrapping other file readers whos read method may not be very efficient   A more detailed description can be found in the Java APIs   Toolkit s use of BufferedReader is probably what you need

User · Answer

Here is some example code to help you get started:

package com.acme;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class FileArrayProvider {

    public String[] readLines(String filename) throws IOException {
        FileReader fileReader = new FileReader(filename);
        BufferedReader bufferedReader = new BufferedReader(fileReader);
        List<String> lines = new ArrayList<String>();
        String line = null;
        while ((line = bufferedReader.readLine()) != null) {
            lines.add(line);
        }
        bufferedReader.close();
        return lines.toArray(new String[lines.size()]);
    }
}

And an example unit test:

package com.acme;

import java.io.IOException;

import org.junit.Test;

public class FileArrayProviderTest {

    @Test
    public void testFileArrayProvider() throws IOException {
        FileArrayProvider fap = new FileArrayProvider();
        String[] lines = fap
                .readLines("src/main/java/com/acme/FileArrayProvider.java");
        for (String line : lines) {
            System.out.println(line);
        }
    }
}

Hope this helps.

User · Answer

You should be able to use forward slashes in Java to refer to file locations   The BufferedReader class is used for wrapping other file readers whos read method may not be very efficient   A more detailed description can be found in the Java APIs   Toolkit s use of BufferedReader is probably what you need

User · Answer

Apache Commons I O provides FileUtils readLines    which should be fine for all but huge files  http   commons apache org io api-release index html  The 2 1 distribution includes FileUtils lineIterator    which would be suitable for large files  Google s Guava libraries include similar utilities

User · Answer

import java io File   import java nio charset Charset  import java nio file Files  import java nio file Path   import java util List           Path filePath   new File  fileName   toPath    Charset charset   Charset defaultCharset            List lt String gt  stringList   Files readAllLines filePath  charset   String   stringArray   stringList toArray new String

User · Answer

You should be able to use forward slashes in Java to refer to file locations   The BufferedReader class is used for wrapping other file readers whos read method may not be very efficient   A more detailed description can be found in the Java APIs   Toolkit s use of BufferedReader is probably what you need

User · Answer

import java io File   import java nio charset Charset  import java nio file Files  import java nio file Path   import java util List           Path filePath   new File  fileName   toPath    Charset charset   Charset defaultCharset            List lt String gt  stringList   Files readAllLines filePath  charset   String   stringArray   stringList toArray new String

User · Answer

Here is some example code to help you get started:

package com.acme;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class FileArrayProvider {

    public String[] readLines(String filename) throws IOException {
        FileReader fileReader = new FileReader(filename);
        BufferedReader bufferedReader = new BufferedReader(fileReader);
        List<String> lines = new ArrayList<String>();
        String line = null;
        while ((line = bufferedReader.readLine()) != null) {
            lines.add(line);
        }
        bufferedReader.close();
        return lines.toArray(new String[lines.size()]);
    }
}

And an example unit test:

package com.acme;

import java.io.IOException;

import org.junit.Test;

public class FileArrayProviderTest {

    @Test
    public void testFileArrayProvider() throws IOException {
        FileArrayProvider fap = new FileArrayProvider();
        String[] lines = fap
                .readLines("src/main/java/com/acme/FileArrayProvider.java");
        for (String line : lines) {
            System.out.println(line);
        }
    }
}

Hope this helps.

User · Answer

You should be able to use forward slashes in Java to refer to file locations   The BufferedReader class is used for wrapping other file readers whos read method may not be very efficient   A more detailed description can be found in the Java APIs   Toolkit s use of BufferedReader is probably what you need

User · Answer

Here is some example code to help you get started:

package com.acme;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class FileArrayProvider {

    public String[] readLines(String filename) throws IOException {
        FileReader fileReader = new FileReader(filename);
        BufferedReader bufferedReader = new BufferedReader(fileReader);
        List<String> lines = new ArrayList<String>();
        String line = null;
        while ((line = bufferedReader.readLine()) != null) {
            lines.add(line);
        }
        bufferedReader.close();
        return lines.toArray(new String[lines.size()]);
    }
}

And an example unit test:

package com.acme;

import java.io.IOException;

import org.junit.Test;

public class FileArrayProviderTest {

    @Test
    public void testFileArrayProvider() throws IOException {
        FileArrayProvider fap = new FileArrayProvider();
        String[] lines = fap
                .readLines("src/main/java/com/acme/FileArrayProvider.java");
        for (String line : lines) {
            System.out.println(line);
        }
    }
}

Hope this helps.

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