从文本文件中查找 MIN/MAX/SUM

Question

输入文本文件：

最小值：1,2,3,5,6

最大：1,2,3,5,6

平均：1,2,3,5,6

从文本文件中的数字列表中获取 MIN/MAX 和 SUM。

package net.codejava;

import java.io.FileReader;
import java.util.Scanner;
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Formatter;

public class MyFile {
       public static int[] toIntArray(String input, String delimiter) {

            return  Arrays.stream(input.split(delimiter)).mapToInt(Integer::parseInt).toArray();
    }
    public static void main(String[] args) throws FileNotFoundException {
        //Declare Variables
        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE;
        double avg = 0.0;
        int sum = 0;
        int count = 0;
        String[] numArray = new String[30];
        int[] maxArray;
        int[] minArray;
        int[] sumArray;

        try {
            //Read the text file ('input.txt')
            String myFile = "input.txt";
            Scanner input = new Scanner(new FileReader(myFile));    
            while(input.hasNext()) {
                input.next();
                numArray[count] = input.next();
                count++;
                }
        } catch(FileNotFoundException e) {
            System.out.println("File not found!");  
        }

        minArray = toIntArray(numArray[0],",");
        maxArray = toIntArray(numArray[1],",");
        sumArray = toIntArray(numArray[2],",");
        
        System.out.println(" Min Value " + Arrays.stream(minArray).min().getAsInt());
        System.out.println(" Max Value " + Arrays.stream(maxArray).max().getAsInt());
        System.out.println(" Sum Value " + Arrays.stream(sumArray).sum());
    }
}

期望的输出：

[1, 2, 3, 5, 6] 的最小值为 1

[1, 2, 3, 5, 6] 的最小值是 6

[1, 2, 3, 5, 6] 的平均值是 3.4

电流输出：

Exception in thread "main" java.util.NoSuchElementException

    at java.base/java.util.Scanner.throwFor(Scanner.java:937)

    at java.base/java.util.Scanner.next(Scanner.java:1478)

    at net.codejava.MyFile.main(MyFile.java:32)

Answer 1

在读取和写入文件时，请务必在处理完成后始终关闭资源。您可以找到多种方法来做到这一点。有关处理资源的信息，请参阅https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html。

    File fileName = new File("input.txt");

    try(FileReader fileReader = new FileReader(fileName);
        BufferedReader bufferedReader = new BufferedReader(fileReader);){

        String input = bufferedReader.readLine();

        while(input != null) {
            //Do something... text file will be of type String.
            input = bufferedReader.readLine();
        }

    } catch (FileNotFoundException e){
        System.out.println("File not found " + fileName.getName());
    } catch (IOException e) {
        System.out.println("Error processing file  " + fileName.getName());
    }

Answer 2

您可以将 while 循环中的条件替换为：while(input.hasNext()) { 并检查输入是否为 int

Answer 3

也许使用 Arrays.stream 方法解决此问题的最简单方法之一如下，

文件格式：

Min:1,2,3,5,6
Max:1,2,7,5,6
Avg:1,2,3,5,6

Java 代码：

package org.personal.TestProject;


import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;
import java.io.FileReader;


public final class MinMaxAvg {


    public static int[] toIntArray(String input, String delimiter) {

        return  Arrays.stream(input.split(delimiter))
                .mapToInt(Integer::parseInt)
                .toArray();
    }

    public static void main(String[] args) throws FileNotFoundException {
//Declare Variables
        int min ;
        int max ;
        double avg ;
        int sum;
        int count = 0;
        String[] numArray = new String[3];
        int[] maxArray;
        int[] minArray;
        int[] sumArray;

//Read the text file ('input.txt')

            String fileName = "input.txt";
            Scanner input = new Scanner(new FileReader(fileName));

//Read the numbers. Get count.
        while (input.hasNext()) {
            numArray[count] = input.next();
            count++;
        }

// Convert the comma seperated string to Int array after removing Min:, Max: and Avg: pattern from the string

        minArray = toIntArray(numArray[0].replaceAll("Min:",""),",");
        maxArray = toIntArray(numArray[1].replaceAll("Max:",""),",");
        sumArray = toIntArray(numArray[2].replaceAll("Avg:",""),",");

// Use arrays.stream to find min,max,sum and average. Sum and average is generated for last line

        min = Arrays.stream(minArray).min().getAsInt();
        max = Arrays.stream(maxArray).max().getAsInt();
        sum = Arrays.stream(sumArray).sum();
        avg = Arrays.stream(sumArray).average().getAsDouble();

        System.out.println(" Min Value     " + min);
        System.out.println(" Max Value     " + max);
        System.out.println(" Sum Value     " + sum);
        System.out.println(" Average Value " + avg);


    }
}

输出如下，

 Min Value     1
 Max Value     7
 Sum Value     17
 Average Value 3.4

Answer 4

package MyFile;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
import java.util.Arrays;
import java.io.PrintWriter;

public class MinMaxAvg {
    public static void main(String[] args) {

        // Create File object
        try {
            File fileName = new File("input.txt");
            File output = new File("output.txt");
            
            //Create Scanner to read file
            Scanner scnr = new Scanner(fileName);
            
            //Output the file line by line
            PrintWriter writer = new PrintWriter(output);
            
            //Read each line of file using Scanner class
            while (scnr.hasNextLine()) {
                String line = scnr.nextLine();

                // split the line and place them in an array.
                int[] numList = splitString(line);
                                
                if (line.toLowerCase().startsWith("min")) {
                    getMin(numList, writer);
                    } else if (line.toLowerCase().startsWith("max")) {
                        getMax(numList, writer);
                    } else if (line.toLowerCase().startsWith("avg")) {
                        getAverage(numList, writer);
                    } else if (line.toLowerCase().startsWith("p")) {
                        getPercentile(numList, line, writer);
                    } else if (line.toLowerCase().startsWith("sum")) {
                        getSum(numList, writer);
                    }
            }
            writer.close();


        } catch (FileNotFoundException e) {
            System.out.println(e + "File not found" );
            return; 
        }

    }
    //End main class
    
    // Class to split 
    public static int[] splitString(String line) {
        // trim the blank spaces on the line
        String shorterLine = line.substring(4).trim();
        
        //split the string 
        String[] list = shorterLine.split(",");
        int listLen = list.length;
        
        // Create an array and iterate through the numbers list
        int[] numList = new int[listLen];
        for (int i = 0; i != listLen; i++) {
            numList[i] = Integer.parseInt(list[i]);
        }
        return numList;
    }
    
    //Calculate the average number
    public static void getAverage(int[] numList, PrintWriter writer) {
        
        //calculate the sum of the array numbers
        int sum = 0;
        for (int i = 0; i < numList.length; i++) {
            sum = sum + numList[i];
        }

        float average = sum / numList.length; 

        // Write average number to file 
        writer.format("The average of " + Arrays.toString(numList) + " is %.1f\n", average);

    }
    
    //calculate the sum 
    public static void getSum(int[] numList, PrintWriter writer) {
        // Iterate through the array 
        int sum = 0;
        for (int i = 0; i < numList.length; i++) {
            sum = sum + numList[i];
        }

        // Write sum to file
        writer.println("The sum of " + Arrays.toString(numList) + " is " + sum);
    }
    
    // Get min number
    public static void getMin(int[] numList, PrintWriter writer) {
        int min = numList[0]; 
        for (int i = 1; i < numList.length; i++) {
            if (numList[i] < min) {
                min = numList[i];
            }
        }
        
        //Write to file
        writer.println("The min of " + Arrays.toString(numList) + " is " + min);

    }
    
    // Get Max number
    public static void getMax(int[] numList, PrintWriter writer) {
       
        int max = numList[0];
        for (int i = 1; i < numList.length; i++) {
            if (numList[i] > max) {
                max = numList[i];
            }
        }
        
      //Write to file
        writer.println("The max of " + Arrays.toString(numList) + " is " + max);
    }
    
    
    // Get percentile
    public static void getPercentile(int[] numList, String line, PrintWriter writer) {
        // sort the array
        Arrays.sort(numList); 
     
        int parsedInteger = Integer.parseInt(line.substring(1, 3));
        
        // cast to float and divide by 100 to get the percentile
        float percentile = (float) parsedInteger / 100;
        
        // Calculate the index position for percentile
        // minus 1 to accommodate the fact that indexing is from 0
        int indexPercentile = (int) (numList.length * percentile) - 1; 

        //Write to file
        writer.format("The %.0f" + "th percentile of " + Arrays.toString(numList)
                + " is " + numList[indexPercentile] + "\n", percentile * 100);
    }
    
    

}

   

Answer 5

您可以简单地从IntStream::summaryStatistics 中使用IntSummaryStatistics。

import java.io.*;
import java.util.*;
import java.util.stream.*;
public class Main {
  public static void main(String[] args) {
    IntSummaryStatistics statistics = intsFromStream(System.in)
        .summaryStatistics();
    System.out.printf("min: %d%nmax: %d%nsum: %d%navg: %.2f%n",
        statistics.getMin(),
        statistics.getMax(),
        statistics.getSum(),
        statistics.getAverage()
      );
  }
  private static IntStream intsFromStream(InputStream in) {
    Scanner scanner = new Scanner(in);
    Spliterator<String> spliterator = Spliterators.spliterator(scanner, Long.MAX_VALUE, Spliterator.ORDERED | Spliterator.NONNULL);
    return StreamSupport.stream(spliterator, false)
        .onClose(scanner::close)
        .mapToInt(Integer::valueOf);
  }
}

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