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I am interating through classes in a Jar file and wish to find those which are not abstract. I can solve this by instantiating the classes and trapping InstantiationException but that has a performance hit as some classes have heavy startup. I can't find anything obviously like isAbstract() in the Class.java docs.

peter.murray.rust
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3 Answers3

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It'll have abstract as one of its modifiers when you call getModifiers() on the class object.

This link should help.

 Modifier.isAbstract( someClass.getModifiers() );

Also:

http://java.sun.com/javase/6/docs/api/java/lang/reflect/Modifier.html

http://java.sun.com/javase/6/docs/api/java/lang/Class.html#getModifiers()

seth
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    Thanks! One little note: You can't use "class" as a variable name, maybe you want to change your example. – Tim Büthe Nov 24 '10 at 17:07
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    @seth I think it should be `Modifier.isAbstract( someClass.class.getModifiers() );` maybe you want to change that – steven7mwesigwa Jan 05 '19 at 00:36
  • According to normal Java naming conventions it is either `someClass.getModifiers()` or `SomeClass.class.getModifiers()` where `Class someClass = SomeClass.class;` – neXus Jan 23 '19 at 14:48
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Class myClass = myJar.load("classname");
bool test = Modifier.isAbstract(myClass.getModifiers());
Stobor
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public static boolean isInstantiable(Class<?> clz) {
    if(clz.isPrimitive() || Modifier.isAbstract( clz.getModifiers()) ||clz.isInterface()  || clz.isArray() || String.class.getName().equals(clz.getName()) || Integer.class.getName().equals(clz.getName())){
        return false;
    }
    return true;
}
Abdushkur Ablimit
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