从 Java 中的文件中读取一组数字，设置为 1 到 3、4 到 16

Question

In a loop, I want to read numbers from a csv file having n numbers of rows. In each iteration of the loop I want to start from the next set of numbers where the previous set was ended. For example, my file has numbers 1, 2, 3, 4........N

Lets say, I want to read 3 numbers in each iteration or any value that user defines to read in each iteration. Iteration 1: Number 1, 2, 3 Iteration 2: Number 4, 5, 6

Here is the sample code that I tried

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class FileReadTest {

    public static void main(String[] args) throws IOException {

        for (int z = 1; z <= 5; z++) {
            System.out.println("File Read Test Iteration "+z);
            BufferedReader bufferedReader = new BufferedReader(new FileReader("testNumbers.csv"));
            String line = bufferedReader.readLine();
            String testString = "Start of the string";

            int rowCount = 3; //5
            int itr = 1;
            int l = 1;
            while (line != null && itr <= (l * rowCount)) {
                itr++;
                testString += "{" + line.split(",")[0] + "}";
                line = bufferedReader.readLine();
                if (itr < (l * rowCount + 1)) testString += ",";
            }
            l++;
        testString += "end of the string";
        System.out.println(testString);
        bufferedReader.close();

    }
}

}

Currently I am getting out as:

File Read Test Iteration 1
Start of the string{1},{2},{3}end of the string
File Read Test Iteration 2
Start of the string{1},{2},{3}end of the string
File Read Test Iteration 3
Start of the string{1},{2},{3}end of the string
File Read Test Iteration 4
Start of the string{1},{2},{3}end of the string
File Read Test Iteration 5
Start of the string{1},{2},{3}end of the string

I want the output as something like:

File Read Test Iteration 1
Start of the string{1},{2},{3}end of the string
File Read Test Iteration 2
Start of the string{4},{5},{6}end of the string
File Read Test Iteration 3
Start of the string{7},{8},{9}end of the string
File Read Test Iteration 4
Start of the string{10},{11},{12}end of the string
File Read Test Iteration 5
Start of the string{13},{14},{15}end of the string

My file looks like enter image description here

Any help is greatly appreciated.

Answer 1

set testString to "" (the empty string) after printing it ( testString = ""; ).

System.out.println("test string is " + testString);
testString = "";
l++;

full code:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class FileReadTest {

    public static void main(String[] args) throws IOException {


        System.out.println("File Read Test");
        BufferedReader bufferedReader = new BufferedReader(new FileReader("testNumbers.csv"));
        String line = bufferedReader.readLine();
        String testString = "";

        int rowCount = 3; //Based on this variable, the number of items to picked in each iteration
        int itr = 1;
        int l = 1;

        for (int z = 1; z <= 5; z++) {

            while (line != null && itr <= (l * rowCount)) {
                itr++;
                testString += "{" + line.split(",")[0] + "}";
                line = bufferedReader.readLine();
            }
            System.out.println("test string is " + testString);
            testString = "";
            l++;
        }
        bufferedReader.close();
    }
}

Output:

File Read Test
test string is {1}{2}{3}
test string is {4}{5}{6}
test string is {7}{8}{9}
test string is {10}{11}{12}
test string is {13}{14}{15}

Answer 2

you almost do it, you just need restart the string

    System.out.println("File Read Test");
    BufferedReader bufferedReader = new BufferedReader(new FileReader("/Users/cesarjesusgutierrez/Downloads/test.csv"));
    String line = bufferedReader.readLine();
    String testString = ""; 

    int rowCount = 3; //Based on this variable, the number of items to picked in each iteration
    int itr = 1;
    int l = 1;

    for (int z = 1; z <= 5; z++) {

        testString = ""; // check this :)
        while (line != null && itr <= (l * rowCount)) {
            itr++;
            testString += "{" + line.split(",")[0] + "}";
            line = bufferedReader.readLine();
        }
        System.out.println("test string is " + testString);
        l++;
    }
    bufferedReader.close();