java - 无法在 Java 中使用 orElseThrow 抛出自定义异常

Question

我尝试使用三元运算和 orElseThrow 抛出自定义异常，如下所示:

public static MainProviderType getMainProviderType(ProviderType providerType) {
    return Optional.ofNullable(MainProviderType.valueOf(providerType.name()))
        .orElseThrow(() -> new ProviderTypeNotFoundException(providerType.name()));
}

但是，当 providerType 为 null 时，此方法返回 NullPointerException 而不是 ProviderTypeNotFoundException。我认为问题与此有关；它无法评估 MainProviderType.valueOf(providerType.name())，因为 providerType.name()。真的吗？我应该如何使用它并解决问题？

Answer 1

public static MainProviderType getMainProviderType(ProviderType providerType) {
    return Optional.ofNullable(providerType)
    .map(ProviderType::name)
    .map(MainProviderType::valueOf)
    .orElseThrow(() -> new ProviderTypeNotFoundException("some message"));
}

更新带有测试用例的完整示例

    private enum ProviderType {
        ONE,
        TWO
    }

    private enum MainProviderType {
        ONE,
        TWO,
        THREE
    }

    public MainProviderType getMainProviderType(ProviderType providerType) {
        return Optional.ofNullable(providerType)
            .map(ProviderType::name)
            .map(MainProviderType::valueOf)
            .orElseThrow();
    }

    @Test
    void selectMainProviderType() {
        var mainProviderType = getMainProviderType(ProviderType.ONE);

        assertEquals(MainProviderType.ONE, mainProviderType);
    }