JUnit4（assertEquals）说对象不同，当它们相同时？

Question

I'm testing my code using JUnit4 to see if an insertion sort of an array of objects ( Word(String a, int b) ) is correctly sorting the array. The problem I'm having is that when I run JUnit it fails, giving me an error: "expected {One, 1} but was {One, 1}." If I print out both values I'm comparing before I run the test they are also the same. The code is:

package sort;

import static org.junit.Assert.*;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class InsertionTest {
    private Word word1;
    private Word word2;
    private Word word3;
    private Word word4;
    private Word wordExpected1;
    private Word wordExpected2;
    private Word wordExpected3;
    private Word wordExpected4; 

    @Before
    public void setUp() throws Exception {
        word1 = new Word("One", 1);
        word2 = new Word("Two", 2);
        word3 = new Word("Three", 3);
        word4 = new Word("Four", 4);
        wordExpected1 = new Word("One", 1);
        wordExpected2 = new Word("Two", 2);
        wordExpected3 = new Word("Three", 3);
        wordExpected4 = new Word("Four", 4);
    }

    @After
    public void tearDown() throws Exception {
    }

    @SuppressWarnings("deprecation")
    @Test
    public void test() {
        Word[] wordList = { word3, word2, word4, word1 };
        Word[] expected = { wordExpected1, wordExpected2, wordExpected3, wordExpected4 };
        Insertion.sortInsert(wordList);
        assertEquals(expected, wordList);
    }
}

The code for the insertionsort:

package sort;
public class Insertion {
/**
 * regular insertion sort
 * @param x - the input array containing scores of words that need to be sorted.
 */
    public static void sortInsert ( Word[] x) {
        int N = x.length;

        for (int i = 1; i < N; i++){
            int tempScore = x[i].getScore();
            String tempWord = x[i].getWord();
            int j;

            for (j = (i - 1); j >= 0 && tempScore < x[j].getScore(); j--){
                x[j + 1].setScore(x[j].getScore());
                x[j + 1].setWord(x[j].getWord());
            }

            x[j + 1].setScore(tempScore);
            x[j + 1].setWord(tempWord);
        }
    }
}

The code for the ADT:

package sort; 
public class Word implements Comparable<Word>{
    private String word;
    private int score;

    public Word(String w, int s){
        this.word = w;
        this.score = s;
    }

    public int getScore(){
        return score;
    }

    public void setScore(int s){
        score = s;
    }

    public String getWord(){
        return word;
    }

    public void setWord(String w){
        word = w;
    }

    @Override
    public int compareTo(Word w){
        if ((this.score) > (w.score)) { return 1; }
        else if ((this.score) < (w.score)) { return -1; }
        return 0;
    }

    public String toString(){
        return ("{" + this.word + "," + this.score + "}");
    }
}

Any help would be appreciated, thank you!

Answer 1

You're creating two different objects. Just because their attributes have the same value, they are not necessarily equal. To achive this, you need to override the equals() method in class Word .

Thus, add:

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Word other = (Word) obj;
        if (score != other.score)
            return false;
        if (word == null) {
            if (other.word != null)
                return false;
        } else if (!word.equals(other.word))
            return false;
        return true;
    }

Eclipse provides an easy way to do this (semi-)automatically. Open your Word class, select Source -> Generate hashCode() and equals()... Select attributes that should be considered when checking two Word objects for equality.

Also, you should oderride hashCode() . Related questions:

• Why should I override hashCode() when I override equals() method?
• What issues should be considered when overriding equals and hashCode in Java?

By the way: Might be a copy&paste issue, but implemented methods from interfaces are not being annotated with @Override (as your compareTo() is). @Override annotation would be appropriate for toString() since you override the toSting() -method of class Object .

From @Override Javadoc:

Indicates that a method declaration is intended to override a method declaration in a supertype.

Answer 2

JUnit's assertEquals depends on you correctly implementing Object.equals(Object) , which you didn't do. Implement equals(Object) in Word to make this work.

Answer 3

Use Lombok to generate the equal and hashcode method. Then it will work. Your code will also become clean by using Lombok annotations.