java 如何检查对象是否是某种类型的数组
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How to check if an object is an array of a certain type
提问by One Two Three
I have an object Field field.
我有一个对象Field field。
I'd like to check if fieldis either an object of type Fooor an array: Foo[].
我想检查field是类型对象Foo还是数组：Foo[]。
Psuedo code:
伪代码：
if field.getType() is Foo || field.getType is Foo[]
Is this possible?
这可能吗？
I've tried
我试过了
if (field.getType().isArray())
// do something
But this would only allow me to check if fieldis an array.
但这只会让我检查是否field是一个数组。
Doing this, on the contrary, will only check if it's an object of Foo
相反，这样做只会检查它是否是 Foo
if (Foo.class.isAssignableFrom(field.getType())
// do something
Any idea how to do this?
知道如何做到这一点吗？
Thanks.
谢谢。
回答by Claas Wilke
Here is some code I used once to handle arrays of all primitive types in Java. As they do not extend the Object class, an instanceof check for Object[] is insufficent.
这是我曾经用来处理 Java 中所有原始类型数组的一些代码。由于它们不扩展 Object 类，因此对 Object[] 的 instanceof 检查是不够的。
/* Check if the given object is an array. */
if (object.getClass().isArray()) {
Class<?> componentType;
componentType = object.getClass().getComponentType();
if (componentType.isPrimitive()) {
if (boolean.class.isAssignableFrom(componentType)) {
for (boolean anElement : (boolean[]) object) {
/* ... */
}
}
else if (byte.class.isAssignableFrom(componentType)) {
/* ... */
}
else if (char.class.isAssignableFrom(componentType)) {
/* ... */
}
else if (double.class.isAssignableFrom(componentType)) {
/* ... */
}
else if (float.class.isAssignableFrom(componentType)) {
/* ... */
}
else if (int.class.isAssignableFrom(componentType)) {
/* ... */
}
else if (long.class.isAssignableFrom(componentType)) {
/* ... */
}
else if (short.class.isAssignableFrom(componentType)) {
/* ... */
}
/* No else. No other primitive types exist. */
}
else {
/* Do something with Object[] here. */
}
}
回答by dnc253
Assuming the Field you mention is a java.lang.reflect.Field, you can just do
假设你提到的 Field 是 a java.lang.reflect.Field，你可以做
field.getType().equals(Foo.class) || field.getType().equals(Foo[].class)
回答by Ixx
Simple compare should work
简单的比较应该有效
import java.lang.reflect.Field;
public class Main {
String[] myStringArray;
String[] myStringArray2;
Object[] myObjectArray;
String str;
public static void main(String... args) {
Field[] flds = Main.class.getDeclaredFields();
for (Field f : flds) {
Class<?> c = f.getType();
if (c == String[].class) {
System.out.println("field" + f.getName() + " is String[]");
}
if (c == String.class) {
System.out.println("field" + f.getName() + " is String");
}
if (c == Object[].class) {
System.out.println("field" + f.getName() + " is Object[]");
}
}
}
}
}
回答by smcg
if (field instanceof Object[])
That should do it.
那应该这样做。
回答by Mark Peters
Since array types are reified, you can just use
由于数组类型被具体化，您可以只使用
if ( field.getType() == Foo.class || field.getType() == Foo[].class ) {
}
Full example:
完整示例：
public class Scratchpad {
String[] strings;
public static void main(String[] args) throws NoSuchFieldException {
if (Scratchpad.class.getDeclaredField("strings").getType() == String[].class) {
System.out.println("They're Strings!");
}
if (Scratchpad.class.getDeclaredField("strings").getType() == Long[].class) {
System.out.println("They're Longs!");
}
}
}
回答by Kennet
I would do something like this:
我会做这样的事情：
public static void main(String[] args) {
Foo foo = new Foo();
Foo[] other = new Foo[1];
other[0] = new Foo();
System.out.println(isFooOrArrayOfFoo(foo));
System.out.println(isFooOrArrayOfFoo(other[0]));
System.out.println(isFooOrArrayOfFoo(new Object()));
}
private static boolean isFooOrArrayOfFoo(Object o) {
return (o instanceof Foo || o.getClass().equals(Foo.class) && o.getClass().isArray());
}
