如何从ArrayList中获取特定元素

Question

import java.util.*;
import java.io.*;

public class Main {
    public static int processData(ArrayList<String> array) {
      for (String elem :array){
       System.out.println(elem);
      }

        return 0;
    }

    public static void main (String[] args) {
        ArrayList<String> inputData = new ArrayList<String>();
        try {
            Scanner in = new Scanner(new BufferedReader(new FileReader("input.txt")));
            while(in.hasNextLine()) {
                String line = in.nextLine().trim();
                if (!line.isEmpty()) // Ignore blank lines
                    inputData.add(line);
            }
            int retVal = processData(inputData);
            PrintWriter output = new PrintWriter(new BufferedWriter(new FileWriter("output.txt")));
            output.println("" + retVal);
            output.close();
        } catch (IOException e) {
            System.out.println("IO error in input.txt or output.txt");
        }
    }
}

282, ij, 11, 1600000
273, cbg, 12, 800000
567, nj, 11, 800000
539, cb, 11, 600000

11 520000

Answer 1

提示

您可以这样计算指数11的平均数值：

public static int processData(ArrayList<String> array) {
    String[] spl;
    int avg = 0, nbr = 0;

    for (String elem : array) {
        //split your String with ", " and space
        spl = elem.split(", ");
        //the index exist in the 3ed position, so you have to check your index if 11 then you can get its value
        if(spl[2].equals("11")){
            avg+=Integer.parseInt(spl[3]);
            nbr++;
        }
        System.out.println(elem);
    }
    System.out.println((avg/nbr));
    return avg / nbr;
}

在代码中打印时，必须使用：

output.println("11 " + retVal);