Java：如何确定类型是原始类型/包装器/字符串还是其他类型
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Java: How to determine if type is any of primitive/wrapper/String, or something else
提问by Ondra ?i?ka
Is there a single method in JDK or common basic libraries which returns true if a type is a primitive, a primitive wrapper, or a String?
如果类型是原始类型、原始包装器或字符串，JDK 或通用基本库中是否有单个方法返回 true？
I.e.
IE
Class<?> type = ...
boolean isSimple = SomeUtil.isSimple( type );
The need for such information can be e.g. to check whether some data can be represented in formats like JSON. The reason for a single method is to be able to use it in expression language or templates.
对此类信息的需求可以是例如检查某些数据是否可以以 JSON 等格式表示。单一方法的原因是能够在表达式语言或模板中使用它。
回答by Ondra ?i?ka
I found something:
我发现了一些东西：
Commons Lang: (would have to combine with check for String)
Commons Lang：（必须结合检查字符串）
ClassUtils.isPrimitiveOrWrapper()
春天:
BeanUtils.isSimpleValueType()
This is what I want, but would like to have it in Commons.
这就是我想要的，但希望在 Commons 中拥有它。
回答by Boann
Is there a single method which returns true if a type is a primitive
如果类型是原始类型，是否有一个返回 true 的方法
Class<?> type = ...;
if (type.isPrimitive()) { ... }
Note that void.class.isPrimitive()is true too, which may or may not be what you want.
请注意，这void.class.isPrimitive()也是正确的，这可能是您想要的，也可能不是。
a primitive wrapper?
原始包装器？
No, but there are only eight of them, so you can check for them explicitly:
不，但只有八个，因此您可以明确检查它们：
if (type == Double.class || type == Float.class || type == Long.class ||
type == Integer.class || type == Short.class || type == Character.class ||
type == Byte.class || type == Boolean.class) { ... }
a String?
一个字符串？
Simply:
简单地：
if (type == String.class) { ... }
That's not one method. I want to determine whether it's one of those named or something else, in one method.
那不是一种方法。我想用一种方法确定它是那些命名的还是其他的。
Okay. How about:
好的。怎么样：
public static boolean isPrimitiveOrPrimitiveWrapperOrString(Class<?> type) {
return (type.isPrimitive() && type != void.class) ||
type == Double.class || type == Float.class || type == Long.class ||
type == Integer.class || type == Short.class || type == Character.class ||
type == Byte.class || type == Boolean.class || type == String.class;
}
回答by icza
The java.util.Classtype has the proper methods:
该java.util.Class类型具有适当的方法：
Class<?> type = ...
boolean primitive = type.isPrimitive();
boolean string_ = type == String.class;
boolean array = type.isArray();
boolean enum_ = type.isEnum();
boolean interf_ = type.isInterface();
回答by Joachim Sauer
Guava provides the Primitivesclass with Primitives.isWrapperType(class)which returns truefor Integer, Long, ...
番石榴提供了Primitives类Primitives.isWrapperType(class)返回true的Integer，Long...
回答by CarlosZ
Integer, Float, Character, etc are not primitives; they are wrapper classes which serve as containers for primitives. They are reference objects. True primitives are types like int, float, double, long, byte, char, and boolean -- non-object types. There's a big difference, since
Integer、Float、Character 等不是基元；它们是包装类，用作原语的容器。它们是参考对象。真正的原语是像 int、float、double、long、byte、char 和 boolean 这样的类型——非对象类型。有很大的不同，因为
value instanceof Float
Float的值实例
won't even compile if "value" is a primitive. "String" is also not a primitive -- it's a type of object. 'null' is also not a primitive -- it's a literal value.
如果“值”是原始值，甚至不会编译。“String”也不是原始类型——它是一种对象。'null' 也不是原始值——它是一个字面值。
回答by Damian Leszczyński - Vash
No there is not. And should not be. For tree difference question you should provide tree different answers.
不，那里没有。而且不应该。对于树差异问题，您应该提供不同的答案。
public static <T> boolean isPrimitive(Class<T> klass) {
return klass.isPrimitive();
}
public static <T> boolean isString(Class<T> klass) {
return String.class == klass; //String is final therefor you can not extend it.
}
public static <T> boolean isPrimitiveWrapper(Class<T> klass) {
return Character.class == klass || Boolean.class == klass || klass.isAssignableFrom(Number.class);
}
