Creating instance of subclass in Java by c.newInstance()

Question

While creating instance of subclass Y

public class X implements I{
    ...

    ...
    public class Y implements I{
        ...

        ...
    }
}

by

o = c.newInstance();

where c is Y class I am getting this exception:

java.lang.InstantiationException: com.gmail.kubuxu.ms2d.Commands.VersionCommand$CCommand
    at java.lang.Class.newInstance0(Unknown Source)
    at java.lang.Class.newInstance(Unknown Source)
    at com.gmail.kubuxu.ms2d.CommandProcessor.<init>(CommandProcessor.java:22)
    at com.gmail.kubuxu.ms2d.Conns.CommandServerProtocol.<init>(CommandServerProtocol.java:13)
    at com.gmail.kubuxu.ms2d.Conns.ClientConn.run(ClientConn.java:40)
    at java.lang.Thread.run(Unknown Source)

Can someone say what I am doing wrong.

This can't work anyway since the inner class is not static. Instantiation of it requires an outer instance. — AllTooSir, May 16 '13 at 16:25

score 0 · Answer 1 · edited May 23 '17 at 12:18

0

Since Y is non-static inner class of X, you cannot create instance of Y directly

like

Class clazz = Y.class
Y ref = clazz.newInstance();

You need to do as explained in this thread

Class<X> oc = X.class;
Class<?> c = Class.forName("X$Y");
Constructor<?> con = c.getConstructors()[0];
Y i = (Y)con.newInstance(oc.newInstance());
System.out.println(i);

edited May 23 '17 at 12:18

Community

1
1

answered May 16 '13 at 16:26

sanbhat

17,522
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score 0 · Accepted Answer · answered May 16 '13 at 16:27

0

The class Y is a non-static nested class. You can't create it without an instance of the class X.

Depending on your needs, the easiest solution for you might be to make it static:

public static class Y implements I{

answered May 16 '13 at 16:27

Andy Thomas

84,978
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Creating instance of subclass in Java by c.newInstance()

2 Answers2