Mega Code Archive
Java lang InstantiationException
<![CDATA[
import static java.lang.System.out;
import java.lang.reflect.InvocationTargetException;
public class Main {
public Main() {
}
public Main(Integer i) {
}
public Main(Object o) {
out.format("Constructor passed Object%n");
}
public Main(String s) {
out.format("Constructor passed String%n");
}
public static void main(String... args) {
String argType = (args.length == 0 ? "" : args[0]);
try {
Class<?> c = Class.forName("Main");
if ("".equals(argType)) {
// IllegalArgumentException: wrong number of arguments
Object o = c.getConstructor().newInstance("foo");
} else if ("int".equals(argType)) {
// NoSuchMethodException - looking for int, have Integer
Object o = c.getConstructor(int.class);
} else if ("Object".equals(argType)) {
// newInstance() does not perform method resolution
Object o = c.getConstructor(Object.class).newInstance("foo");
} else {
assert false;
}
// production code should handle these exceptions more gracefully
} catch (ClassNotFoundException x) {
x.printStackTrace();
} catch (NoSuchMethodException x) {
x.printStackTrace();
} catch (InvocationTargetException x) {
x.printStackTrace();
} catch (InstantiationException x) {
x.printStackTrace();
} catch (IllegalAccessException x) {
x.printStackTrace();
}
}
}
]]>