将整数转换为长整数 [英] Converting Integer to Long

问题描述

我需要使用反射获得字段的值。这样发生，我不总是确定字段的数据类型。为此，为了避免一些代码重复，我创建了以下方法：

  @SuppressWarnings（unchecked）
 private static< T> throws Throwable {
 Field f = classUnderTest.getDeclaredField（processFieldName（var））; T getValueByReflection（VarInfo var，Class<？> classUnderTest，Object runtimeInstance） 
 f.setAccessible（true）; 
 T value =（T）f.get（runtimeInstance）; 
 
返回值; 
} 
  

并使用此方法：

  Long value1 = getValueByReflection（inv.var1（），classUnderTest，runtimeInstance）; 
  

或

  Double [] value2 = getValueByReflection（inv.var2（），classUnderTest，runtimeInstance）; 
  

问题是我似乎不能转换 Integer 到长：

  java.lang.ClassCastException： java.lang.Integer不能转换为java.lang.Long 
  

有更好的方法来实现

解决方案

不，您不能将 Integer 转换为 Long ，即使您可以从 int 到 long 。对于已知为数字的个体值，您希望获取长值，可以使用：

  Number tmp = getValueByReflection（inv.var1（），classUnderTest，runtimeInstance）; 
 Long value1 = tmp.longValue（）; 
  

对于数组，它会更棘手...

I need to get the value of a field using reflection. It so happens that I am not always sure what the datatype of the field is. For that, and to avoid some code duplication I have created the following method:

@SuppressWarnings("unchecked")
private static <T> T getValueByReflection(VarInfo var, Class<?> classUnderTest, Object runtimeInstance) throws Throwable {
  Field f = classUnderTest.getDeclaredField(processFieldName(var));
  f.setAccessible(true);
  T value = (T) f.get(runtimeInstance);

  return value;
}

And use this method like:

Long value1 = getValueByReflection(inv.var1(), classUnderTest, runtimeInstance);

or

Double[] value2 = getValueByReflection(inv.var2(), classUnderTest, runtimeInstance);

The problem is that I can't seem to cast Integer to Long:

java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.Long

Is there a better way to achieve this?

I am using Java 1.6.

解决方案

No, you can't cast Integer to Long, even though you can convert from int to long. For an individual value which is known to be a number and you want to get the long value, you could use:

Number tmp = getValueByReflection(inv.var1(), classUnderTest, runtimeInstance);
Long value1 = tmp.longValue();

For arrays, it will be trickier...

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