java - 试图解决NoSuchMethodError

Question

我正在尝试在ArrayIntList类中测试public void set(char letter, int value)方法。

public class LetterInventory {
   private int[] count; //list of letters a to z
   private int size;
   public static final int MAX = 26;

   public LetterInventory(String data) {
      count = new int[MAX];
      data = data.toLowerCase();
      size = 0;

      for (int i = 0; i < data.length(); i++) {
         if (Character.isLetter(data.charAt(i))) {
            count[data.charAt(i) - 'a']++;
            size++;
         }
      }
   }

   public int size() {
      return size;
   }

   public boolean isEmpty() {
      return size == 0;
   }

   public int get(char letter) {
      if(!Character.isLetter(letter)) {
         throw new IllegalArgumentException("nonalphabetic character: " + letter);
      }
      return count[Character.toLowerCase(letter) - 'a'];
   }

   public String toString() {
      String represent = "[";

      for (int i = 0; i < MAX; i++) {
         for (int j = 0; j < count[i]; j++) {
            represent += (char) ('a' + i);
         }
      }
      represent += "]";
      return represent;
   }

   public void set(char letter, int value) {
      if (!Character.isLetter(letter) || value < 0) {
         throw new IllegalArgumentException("nonalphabetic character: " + letter,
                                           "negative value " + value);
      }

      letter = Character.toLowerCase(letter);
      size += value - count[letter - 'a'];
      count[letter - 'a'] = value;
   }

   /*
   public LetterInventory add(LetterInventory other) {
      LetterInventory total = new LetterInventory();

   } 
   */
}  

在此类中，set方法将给定字母的计数设置为给定值。

尝试从我的主班测试它时：

// This program tests stage 2 of the LetterInventory class.  The program reads
// from the file test2.txt which has a series of test cases with the correct
// answers.

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

public class Test2 {
    public static void main(String[] args) {
        Scanner input = null;
        try {
            input = new Scanner(new File("test2.txt"));
        } catch (FileNotFoundException e) {
            System.out.println("You must copy test2.txt to this directory" +
                               " before running the testing program.");
            System.exit(1);
        }
        LetterInventory tester = new LetterInventory("");
        System.out.println("Starting with empty inventory");
        check(tester, input);
        while (input.hasNext()) {
            char ch = input.next().charAt(0);
            int count = input.nextInt();
            System.out.println("setting count for " + ch + " to " + count);
            try {
                tester.set(ch, count);
            } catch(Exception e) {
                System.out.println("failed");
                System.out.println("    threw exception: " + e);
                int line = e.getStackTrace()[0].getLineNumber();
                System.out.println("    in LetterInventory line#" + line);
                System.exit(1);
            }
            check(tester, input);
        }
        System.out.println("All tests passed.");
    }

    // pre : input file contains a 2-line test case that contains the state
    //       that the given inventory should be in after performing the given
    //       call on get
    // post: reports whether or not test was passed
    public static void check(LetterInventory tester, Scanner input) {
        testSize(tester, input);
        testToString(tester, input);
        testIsEmpty(tester, input);
        testGet(tester, input);
        System.out.println("size, toString, isEmpty, and count all passed");
        System.out.println();
    }

    // pre : input file contains correct toString
    // post: reports whether or not test was passed
    public static void testToString(LetterInventory tester, Scanner input) {
        String correct = input.next();
        System.out.println("inventory = " + correct);
        String test = "";
        try {
            test = tester.toString();
        } catch (Exception e) {
            System.out.println("toString failed");
            System.out.println("    threw exception: " + e);
            int line = e.getStackTrace()[0].getLineNumber();
            System.out.println("    in LetterInventory line#" + line);
            System.exit(1);
        }
        if (!correct.equals(test)) {
            System.out.println("toString failed");
            System.out.println("    correct toString = " + correct);
            System.out.println("    your toString    = " + test);
            System.exit(1);
        }
    }

    // pre : input file contains correct size
    // post: reports whether or not test was passed
    public static void testSize(LetterInventory tester, Scanner input) {
        int correct = input.nextInt();
        int test = 0;
        try {
            test = tester.size();
        } catch (Exception e) {
            System.out.println("size failed");
            System.out.println("    threw exception: " + e);
            int line = e.getStackTrace()[0].getLineNumber();
            System.out.println("    in LetterInventory line#" + line);
            System.exit(1);
        }
        if (correct != test) {
            System.out.println("size failed");
            System.out.println("    correct size = " + correct);
            System.out.println("    your size    = " + test);
            System.exit(1);
        }
    }

    // pre : input file contains correct isEmpty
    // post: reports whether or not test was passed
    public static void testIsEmpty(LetterInventory tester, Scanner input) {
        boolean correct = input.nextBoolean();
        boolean test = false;
        try {
            test = tester.isEmpty();
        } catch (Exception e) {
            System.out.println("isEmpty failed");
            System.out.println("    threw exception: " + e);
            int line = e.getStackTrace()[0].getLineNumber();
            System.out.println("    in LetterInventory line#" + line);
            System.exit(1);
        }
        if (correct != test) {
            System.out.println("isEmpty failed");
            System.out.println("    correct isEmpty = " + correct);
            System.out.println("    your isEmpty    = " + test);
            System.exit(1);
        }
    }

    // pre : input file contains correct get values (26 of them)
    // post: reports whether or not test was passed
    public static void testGet(LetterInventory tester, Scanner input) {
        for (char ch = 'a'; ch <= 'z'; ch++) {
            int correct = input.nextInt();
            int test = 0;
            try {
                test = tester.get(ch);
            } catch (Exception e) {
                System.out.println("get failed for '" + ch + "'");
                System.out.println("    threw exception: " + e);
                int line = e.getStackTrace()[0].getLineNumber();
                System.out.println("    in LetterInventory line#" + line);
                System.exit(1);
            }
            if (correct != test) {
                System.out.println("get failed for '" + ch + "'");
                System.out.println("    correct get = " + correct);
                System.out.println("    your get    = " + test);
                System.exit(1);
            }
        }
    }
}

我收到以下错误：

Starting with empty inventory
inventory = []
size, toString, isEmpty, and count all passed

setting count for g to 3
Exception in thread "main" java.lang.NoSuchMethodError: LetterInventory.set(CI)V

test2.txt文件供参考：

0 [] true 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
g 3
3 [ggg] false 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
a 2
5 [aaggg] false 2 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
h 4
9 [aaggghhhh] false 2 0 0 0 0 0 3 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
m 1
10 [aaggghhhhm] false 2 0 0 0 0 0 3 4 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
g 0
7 [aahhhhm] false 2 0 0 0 0 0 0 4 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
b 2
9 [aabbhhhhm] false 2 2 0 0 0 0 0 4 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
z 1
10 [aabbhhhhmz] false 2 2 0 0 0 0 0 4 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 1
p 4
14 [aabbhhhhmppppz] false 2 2 0 0 0 0 0 4 0 0 0 0 1 0 0 4 0 0 0 0 0 0 0 0 0 1
z 0
13 [aabbhhhhmpppp] false 2 2 0 0 0 0 0 4 0 0 0 0 1 0 0 4 0 0 0 0 0 0 0 0 0 0
b 0
11 [aahhhhmpppp] false 2 0 0 0 0 0 0 4 0 0 0 0 1 0 0 4 0 0 0 0 0 0 0 0 0 0
a 0
9 [hhhhmpppp] false 0 0 0 0 0 0 0 4 0 0 0 0 1 0 0 4 0 0 0 0 0 0 0 0 0 0
h 0
5 [mpppp] false 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 4 0 0 0 0 0 0 0 0 0 0
p 0
1 [m] false 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
m 0
0 [] true 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
G 3
3 [ggg] false 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
A 2
5 [aaggg] false 2 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
H 4
9 [aaggghhhh] false 2 0 0 0 0 0 3 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
M 1
10 [aaggghhhhm] false 2 0 0 0 0 0 3 4 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0

Answer 1

我在set类的LetterInventory方法的这一行中收到编译器错误：

throw new IllegalArgumentException("nonalphabetic character: " + letter,
                                       "negative value " + value);

解决之后，测试顺利进行。