blocks|key|1839671|text|这应该可以做到：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1839672|public+static+boolean+implementsInterface(Object+object,+Class+interf){
++++return+interf.isInstance(object);
}|code-block|syntax|javascript|1839673|例如,|1839674|+java.io.Serializable.class.isInstance("a+test+string")|1839675|计算结果为true。|offset|length|style|CODE|1839676|entityMap^0|0|0|0|0|5|4|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@$M|X|N|Y|O|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

This should do:

<pre><code>public static boolean implementsInterface(Object object, Class interf){
 return interf.isInstance(object);
}
</code></pre>

For example,

<pre><code> java.io.Serializable.class.isInstance("a test string")
</code></pre>

evaluates to <code>true</code>.

blocks|key|2053948|text|这很简单：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2053949|+++interf.isInstance(object)|code-block|syntax|javascript|2053950|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

that was easy : 

<pre><code> interf.isInstance(object)
</code></pre>

blocks|key|1839826|text|我更喜欢instanceof|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1839827|if+(obj+instanceof+SomeType)+{+...+}|code-block|syntax|javascript|1839828|它比SomeType.isInstance(obj)更常见，也更易读。|1839829|entityMap^0|4|A|0|0|2|O|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

I prefer <code>instanceof</code>:

<pre><code>if (obj instanceof SomeType) { ... }
</code></pre>

which is much more common and readable than <code>SomeType.isInstance(obj)</code>

blocks|key|1839931|text|如果您想要测试接口：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1839932|public+List<myType>+getElement(Class<?>+clazz)+{
++++List<myType>+els+=+new+ArrayList<myType>();
++++for+(myType+e:+this.elements.values())+{
++++++++if+(clazz.isAssignableFrom(e.getClass()))+{
++++++++++++els.add(e);
++++++++}
++++}
++++return+els;|code-block|syntax|javascript|1839933|}|1839934|clazz是一个接口，而myType是您定义的一种类型，它可以实现许多接口。使用此代码，您只能获得实现已定义接口的类型|1839935|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you want to test for interfaces:

<pre><code>public List&lt;myType&gt; getElement(Class&lt;?&gt; clazz) {
 List&lt;myType&gt; els = new ArrayList&lt;myType&gt;();
 for (myType e: this.elements.values()) {
 if (clazz.isAssignableFrom(e.getClass())) {
 els.add(e);
 }
 }
 return els;
</code></pre>

}

clazz is an Interface and myType is a Type that you defined that may implement a number of interfaces. With this code you get only the types that implement a defined interface

blocks|key|1839994|text|使用Apache+commons-lang+ArrayUtils，查看您需要的接口是否包含在对象的接口中|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1839995|public+static+Boolean+implementsInterface(Object+object,+Class+interf){
++++return+ArrayUtils.contains(object.getClass().getInterfaces(),+interf);
}|code-block|syntax|javascript|1839996|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

With Apache commons-lang ArrayUtils, see if the interface you require is contained in the interfaces of you object

<pre><code>public static Boolean implementsInterface(Object object, Class interf){
 return ArrayUtils.contains(object.getClass().getInterfaces(), interf);
}
</code></pre>

blocks|key|2054369|text|今晚我在android上遇到了这个问题，在看了javadoc的解决方案后，我想出了这个真正有效的解决方案，只适合像我这样需要比javadoc解释更多的人。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2054370|这是一个使用android+java的实际界面的工作示例。在尝试转换AboutDialogListener字段之前，它会检查调用实现了AboutDialogListener接口的活动。|2054371|public+class+About+extends+DialogFragment+implements+OnClickListener,
++++OnCheckedChangeListener+{

public+static+final+String+FIRST_RUN_ABOUT+=+"com.gosylvester.bestrides.firstrunabout";


public+interface+AboutDialogListener+{
++++void+onFinishEditDialog(Boolean+_Checked);
}

private+AboutDialogListener+adl;

@Override
public+View+onCreateView(LayoutInflater+inflater,+ViewGroup+container,
++++++++Bundle+savedInstanceState)+{
++++Activity+a+=+this.getActivity();
++++if+(AboutDialogListener.class.isInstance(a))+{
++++++++adl+=+(AboutDialogListener)+a;
++++++++}
}|code-block|syntax|javascript|2054372|..。稍后，我在调用接口之前检查字段adl是否为!null|2054373|@Override
public+void+onStop()+{
++++super.onStop();
++++sharedPref.edit().putBoolean(About.FIRST_RUN_ABOUT,+_Checked).commit();
++++//+if+there+is+an+interface+call+it.
++++if+(adl+!=+null)+{
++++++++adl.onFinishEditDialog(is_Checked());
++++}
}|2054374|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I had this problem tonight with android and after looking at the javadoc solutions I came up with this real working solution just for people like me that need a little more than a javadoc explanation.

Here's a working example with an actual interface using android java.
It checks the activity that called implemented the AboutDialogListener interface
before attempting to cast the AboutDialogListener field.

<pre><code>public class About extends DialogFragment implements OnClickListener,
 OnCheckedChangeListener {

public static final String FIRST_RUN_ABOUT = "com.gosylvester.bestrides.firstrunabout";


public interface AboutDialogListener {
 void onFinishEditDialog(Boolean _Checked);
}

private AboutDialogListener adl;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
 Bundle savedInstanceState) {
 Activity a = this.getActivity();
 if (AboutDialogListener.class.isInstance(a)) {
 adl = (AboutDialogListener) a;
 }
}
</code></pre>

...
Later I check if the field adl is !null before calling the interface

<pre><code>@Override
public void onStop() {
 super.onStop();
 sharedPref.edit().putBoolean(About.FIRST_RUN_ABOUT, _Checked).commit();
 // if there is an interface call it.
 if (adl != null) {
 adl.onFinishEditDialog(is_Checked());
 }
}
</code></pre>

This has probably been asked before, but a quick search only brought up the same question asked for C#. <a href="https://stackoverflow.com/questions/410227/test-if-object-implements-interface">See here.</a>

What I basically want to do is to check wether a given object implements a given interface.

I kind of figured out a solution but this is just not comfortable enough to use it frequently in if or case statements and I was wondering wether Java does not have built-in solution.

<pre><code>public static Boolean implementsInterface(Object object, Class interf){
 for (Class c : object.getClass().getInterfaces()) {
 if (c.equals(interf)) {
 return true;
 }
 }
 return false;
}
</code></pre>

<hr>
EDIT: Ok, thanks for your answers. Especially to Damien Pollet and Noldorin, you made me rethink my design so I don't test for interfaces anymore.

Test if object implements interface

Java

这可能以前有人问过，但快速搜索只会给C#带来同样的问题。我主要想做的是检查给定的对象是否实现了给定的接口。我想出了一个解决方案，但在if或case语句中频繁使用它并不够舒服，我想知道Java是否没有内置的解决方案。public static Boolean implementsInterface(Object obje...

问测试对象是否实现了接口
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