java - 尝试比较同一类中的两个对象时出现 AssertionFailedError 错误(在覆盖 Equals() 和 Hashcode() 之后)

Question

我第一次尝试覆盖我的类(Money)来检查特定属性上的两个对象。我第二次尝试检查同一类中的两个相同对象(金钱)但没有成功。

我尝试了重写 Equals() 和 Hashcode()

第一个类(金钱)。在文件顶部。

    public static final Money HALF_DINAR = new Money(BigDecimal.valueOf(0.50));
public BigDecimal current_Money;
    public static final Money ZERO =new Money(BigDecimal.ZERO);
    public static Money mInsideMachine = new Money(BigDecimal.ZERO);

    @Override
    public boolean equals(Object o) {

        if (o == this) return true;

        if (!(o instanceof Money)) {
            return false;
        }
        Money money = (Money) o;


        return new EqualsBuilder()
                .append(this.current_Money,money.current_Money)
                .isEquals();
    }

    @Override
    /*public int hashCode() {
        return Objects.hash(current_Money);
    }*/
    public int hashCode(){
            return new HashCodeBuilder(17, 37)
                    .append(current_Money)
                    .toHashCode();
    }

我用来检查对象的命令是

 assertThat(snackMachine.moneyInside()).isEqualTo(Money.HALF_DINAR);

*请注意:对象 SnackMachine 来自 SnackMachine 类，但返回值来自 Money 类。这是 MoneyInside 的代码。

    public Money moneyInside() {
        return Money.mInsideMachine;
}

第二个文件的代码(不可更改)(SnackMachine类)单元测试

 @Test
    void buying_a_snack_after_inserting_just_enough_money_then_the_money_inside_should_equals_to_money_inserted() {
        snackMachine.insertMoney(Money.QUARTER_DINAR);
        snackMachine.insertMoney(Money.QUARTER_DINAR);

        snackMachine.buySnack(SnackType.CHEWING_GUM);

        System.out.println("Moneyinside (Unit test)"+Money.mInsideMachine.current_Money.toString());
        System.out.println("Money half dinar (Unit test)"+Money.HALF_DINAR.current_Money.toString());
        //assertThat(snackMachine.moneyInTransaction()).isEqualTo(Money.ZERO);
        assertThat(snackMachine.moneyInside()).isEqualTo(Money.HALF_DINAR);

    }

我添加了一些代码来打印值，输出是:

Moneyinside (Unit test)0.50
Money half dinar (Unit test)0.5


org.opentest4j.AssertionFailedError: 
Expecting:
 <com.progressoft.induction.Money@885>
to be equal to:
 <com.progressoft.induction.Money@311>
but was not.
Expected :com.progressoft.induction.Money@311
Actual   :com.progressoft.induction.Money@885

Answer 1

这里的问题是 0.5 不等于 0.50，除非您使用 isEqualByComparingTo​。请参阅https://docs.oracle.com/javase/8/docs/api/java/math/BigDecimal.html#compareTo-java.math.BigDecimal-

示例:

 // assertion will pass because 8.0 is equal to 8.00 using BigDecimal.compareTo(BigDecimal)
 assertThat(new BigDecimal("8.0")).isEqualByComparingTo(new BigDecimal("8.00"));
 // assertion fails 
 assertThat(new BigDecimal("8.0")).isEqualTo(new BigDecimal("8.00"));