Java 计算小时差的断言失败

我从日历日期中减去

500小时

，我的方法是以小时为单位计算差异

为什么下面的断言失败了

测试方法：

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.set(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

java.lang.AssertionError: expected:<500> but was:<514>
    at org.junit.Assert.fail(Assert.java:88)
    at org.junit.Assert.failNotEquals(Assert.java:834)
    at org.junit.Assert.assertEquals(Assert.java:645)
    at org.junit.Assert.assertEquals(Assert.java:631)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.add(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

测试用例：

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.set(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

java.lang.AssertionError: expected:<500> but was:<514>
    at org.junit.Assert.fail(Assert.java:88)
    at org.junit.Assert.failNotEquals(Assert.java:834)
    at org.junit.Assert.assertEquals(Assert.java:645)
    at org.junit.Assert.assertEquals(Assert.java:631)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.add(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

错误跟踪：

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.set(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

java.lang.AssertionError: expected:<500> but was:<514>
    at org.junit.Assert.fail(Assert.java:88)
    at org.junit.Assert.failNotEquals(Assert.java:834)
    at org.junit.Assert.assertEquals(Assert.java:645)
    at org.junit.Assert.assertEquals(Assert.java:631)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.add(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

java.lang.AssertionError:应为：但为：
位于org.junit.Assert.fail（Assert.java:88）
位于org.junit.Assert.failNotEquals（Assert.java:834）
位于org.junit.Assert.assertEquals（Assert.java:645）
位于org.junit.Assert.assertEquals（Assert.java:631）
在sun.reflect.NativeMethodAccessorImpl.invoke0（本机方法）处

这是一个错误：

ackCal.set(Calendar.HOUR_OF_DAY, -500);

测试方法：

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.set(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

java.lang.AssertionError: expected:<500> but was:<514>
    at org.junit.Assert.fail(Assert.java:88)
    at org.junit.Assert.failNotEquals(Assert.java:834)
    at org.junit.Assert.assertEquals(Assert.java:645)
    at org.junit.Assert.assertEquals(Assert.java:631)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.add(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

测试用例：

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.set(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

java.lang.AssertionError: expected:<500> but was:<514>
    at org.junit.Assert.fail(Assert.java:88)
    at org.junit.Assert.failNotEquals(Assert.java:834)
    at org.junit.Assert.assertEquals(Assert.java:645)
    at org.junit.Assert.assertEquals(Assert.java:631)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

 public long dataFetchTotalTime(long time) {
        long hours = 0;
        Calendar ackCal = Calendar.getInstance();
        long diff = ackCal.getTime().getTime() - time;
        hours = TimeUnit.HOURS.convert(diff, TimeUnit.MILLISECONDS);
        return hours;
    }

@Test
public void checkFetchTimeDiff()
{
    long expected = 500;
    Client client = new Client();
    Calendar ackCal = Calendar.getInstance();
    ackCal.add(Calendar.HOUR_OF_DAY, -500);
    long actual = client.dataFetchTotalTime(ackCal.getTime().getTime());
    Assert.assertEquals(expected, actual);
}

tl；博士 看这个

五百

java.time 您正在使用可怕的日期时间类，这些类在几年前被JSR310中定义的现代java.time类所取代

ZoneDateTime

Calendar

类，实际上它常用的子类，

gregoriacalendar

，被替换为。

ZoneDateTime

类表示通过特定地区的人们使用的挂钟时间看到的一个时刻。换句话说，一个日期，一天中的一个时间，在一个时区的上下文中

您可以根据需要进行转换，但最好完全避免遗留的日期时间类。若要转换，请调用添加到旧类中的新方法

GregorianCalendar gc = ( GregorianCalendar ) myJavaUtilCalendar  ;  // Cast from the more general to the concrete.
ZonedDateTime zdt = gc.toZonedDateTime() ;  // Convert from legacy class to modern class.

要捕获当前时刻，请指定所需的时区。在任何一个特定的时刻，世界各地的日期都因地区而异

ZoneId z = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime zdt = ZonedDateTime.now( z ) ;

持续时间

做你的数学题。以小时-分-秒或年-月-天的比例表示未附加到时间线的时间跨度

Duration d = Duration.ofHours( 500 ) ;
ZonedDateTime zdtLater = zdt.plus( d ) ; 

要确定经过的时间，请使用

要以标准ISO 8601格式查看文本，请调用

toString

String output = elapsed.toString() ;

要以总小时数查看已用时间，请拨打

---

关于java.time 该框架内置于Java8及更高版本中。这些类取代了麻烦的旧日期时间类，例如，&

要了解更多信息，请参阅。并搜索堆栈溢出以获得许多示例和解释。规格是

该项目现已启动，建议迁移到类

您可以直接与数据库交换java.time对象。使用兼容的或更高版本。不需要字符串，也不需要

java.sql.*

类

从哪里获得java.time类

• 、和更高版本-标准Java API的一部分，带有捆绑实现。
  • Java9添加了一些次要功能和修复
• 及
  • 大多数java.time功能都在中向后移植到Java6和Java7
• • 更高版本的Android捆绑包实现了java.time类
  • 对于早期的Android(