How can I open a .txt file and read numbers separated by enters or spaces into an array list?
This question is related to
java
Read file, parse each line into an integer and store into a list:
List<Integer> list = new ArrayList<Integer>();
File file = new File("file.txt");
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader(file));
String text = null;
while ((text = reader.readLine()) != null) {
list.add(Integer.parseInt(text));
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (reader != null) {
reader.close();
}
} catch (IOException e) {
}
}
//print out the list
System.out.println(list);
A much shorter alternative is below:
Path filePath = Paths.get("file.txt");
Scanner scanner = new Scanner(filePath);
List<Integer> integers = new ArrayList<>();
while (scanner.hasNext()) {
if (scanner.hasNextInt()) {
integers.add(scanner.nextInt());
} else {
scanner.next();
}
}
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. Although default delimiter is whitespace, it successfully found all integers separated by new line character.
Good news in Java 8 we can do it in one line:
List<Integer> ints = Files.lines(Paths.get(fileName))
.map(Integer::parseInt)
.collect(Collectors.toList());
import java.io.*;
public class DataStreamExample {
public static void main(String args[]){
try{
FileWriter fin=new FileWriter("testout.txt");
BufferedWriter d = new BufferedWriter(fin);
int a[] = new int[3];
a[0]=1;
a[1]=22;
a[2]=3;
String s="";
for(int i=0;i<3;i++)
{
s=Integer.toString(a[i]);
d.write(s);
d.newLine();
}
System.out.println("Success");
d.close();
fin.close();
FileReader in=new FileReader("testout.txt");
BufferedReader br=new BufferedReader(in);
String i="";
int sum=0;
while ((i=br.readLine())!= null)
{
sum += Integer.parseInt(i);
}
System.out.println(sum);
}catch(Exception e){System.out.println(e);}
}
}
OUTPUT:: Success 26
Also, I used array to make it simple.... you can directly take integer input and convert it into string and send it to file. input-convert-Write-Process... its that simple.
try{
BufferedReader br = new BufferedReader(new FileReader("textfile.txt"));
String strLine;
//Read File Line By Line
while ((strLine = br.readLine()) != null) {
// Print the content on the console
System.out.println (strLine);
}
//Close the input stream
in.close();
}catch (Exception e){//Catch exception if any
System.err.println("Error: " + e.getMessage());
}finally{
in.close();
}
This will read line by line,
If your no. are saperated by newline char. then in place of
System.out.println (strLine);
You can have
try{
int i = Integer.parseInt(strLine);
}catch(NumberFormatException npe){
//do something
}
If it is separated by spaces then
try{
String noInStringArr[] = strLine.split(" ");
//then you can parse it to Int as above
}catch(NumberFormatException npe){
//do something
}
File file = new File("file.txt");
Scanner scanner = new Scanner(file);
List<Integer> integers = new ArrayList<>();
while (scanner.hasNext()) {
if (scanner.hasNextInt()) {
integers.add(scanner.nextInt());
}
else {
scanner.next();
}
}
System.out.println(integers);
Source: Stackoverflow.com