`Class.newInstance()` throws java.lang.StackOverflowError with Reflections

Question

Code:

Reflections reflections = new Reflections("com.erby.tab.tabs");

for(Class<? extends BaseTab> t : reflections.getSubTypesOf(BaseTab.class)) {
    try {
        BaseTab tab = t.newInstance();

        System.out.println(tab.toString());
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

BaseTab.java:

public abstract class BaseTab extends Tab implements Serializable {
    public abstract String getPrefix();

    @Override
    public abstract String toString();
}

HomeTab.java:

public class HomeTab extends BaseTab {
    public HomeTab() {
        setText(toString());
    }

    @Override
    public String getPrefix() {
        return "home";
    }

    @Override
    public String toString() {
        return "Home Tab";
    }
}

When calling this I get:

Caused by: java.lang.StackOverflowError
at sun.misc.URLClassPath.getLoader(URLClassPath.java:476)
at sun.misc.URLClassPath.getNextLoader(URLClassPath.java:457)
at sun.misc.URLClassPath.access$100(URLClassPath.java:64)
at sun.misc.URLClassPath$1.next(URLClassPath.java:239)
at sun.misc.URLClassPath$1.hasMoreElements(URLClassPath.java:250)
at java.net.URLClassLoader$3$1.run(URLClassLoader.java:601)
at java.net.URLClassLoader$3$1.run(URLClassLoader.java:599)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader$3.next(URLClassLoader.java:598)
at java.net.URLClassLoader$3.hasMoreElements(URLClassLoader.java:623)
at sun.misc.CompoundEnumeration.next(CompoundEnumeration.java:45)
at sun.misc.CompoundEnumeration.hasMoreElements(CompoundEnumeration.java:54)
at sun.misc.CompoundEnumeration.next(CompoundEnumeration.java:45)
at sun.misc.CompoundEnumeration.hasMoreElements(CompoundEnumeration.java:54)
at org.reflections.util.ClasspathHelper.forResource(ClasspathHelper.java:61)
at org.reflections.util.ClasspathHelper.forPackage(ClasspathHelper.java:51)
at org.reflections.util.ConfigurationBuilder.build(ConfigurationBuilder.java:93)
at org.reflections.Reflections.<init>(Reflections.java:170)
at org.reflections.Reflections.<init>(Reflections.java:143)
at com.erby.tab.tabs.TestTab.<init>(TestTab.java:20)
at sun.reflect.GeneratedConstructorAccessor2.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at java.lang.Class.newInstance(Class.java:442)
at com.erby.tab.tabs.TestTab.<init>(TestTab.java:24)
at sun.reflect.GeneratedConstructorAccessor2.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at java.lang.Class.newInstance(Class.java:442)
at com.erby.tab.tabs.TestTab.<init>(TestTab.java:24)
at sun.reflect.GeneratedConstructorAccessor2.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
at java.lang.Class.newInstance(Class.java:442)

FYI BaseTab is extending off the javafx Tab.

I found out that it was iterating over every class and creating hundreds of instances before it gets the error. The questing is where is my code going wrong and how can I fix it? Thanks.

Where's the first code snippet located? Is it inside some constructor (or instance initialization block)? — Eran, Jul 03 '15 at 05:36
@Eran The first code is located in the constructor. Just tried it in the main method, it printed the 1st one ("Home") and then the exact same error message appeared. — 3legit4quit, Jul 03 '15 at 05:37
So you have code in your constructor that creates new instances, and thus calls itself. Hence the infinite recursion that ends in stack overflow error. — Eran, Jul 03 '15 at 05:40
@Eran Yes you are right. How stupid I feel after 4 days trying to fix this. — 3legit4quit, Jul 03 '15 at 05:43

score 1 · Accepted Answer · answered Jul 03 '15 at 05:46

1

As you wrote in your comment, the first code snippet appears in a constructor. That snippet creates new instances, which causes that consturctor to be called again. This results in an infinite recursion that ends in stack overflow error.

answered Jul 03 '15 at 05:46

Eran

387,369
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score 0 · Answer 2 · answered Jul 03 '15 at 05:46

0

Loop was in a constructor. Kept on repeating itself.

answered Jul 03 '15 at 05:46

3legit4quit

593
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score 0 · Answer 3 · answered Jul 03 '15 at 06:14

0

I think there is another subclass by name TestTab is repeatedly being initialized from it's constructor. I am seeing this from your error message. Check that out. I am not seeing any such class by name TestTab nevertheless.

answered Jul 03 '15 at 06:14

sakthisundar

3,278
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`Class.newInstance()` throws java.lang.StackOverflowError with Reflections

3 Answers3