cannot use array of Class as listbox or grid model

import java.util.Arrays;

public class TestViewModel {
private final Class<?> classes[] = new Class<?>[] { String.class, Integer.class };

public Class<?>[] getClasses() {
return Arrays.copyOf(classes, classes.length);
}
}

<listbox apply="org.zkoss.bind.BindComposer" viewModel="@id('vm') @init('TestViewModel')"
model="@load(vm.classes)">
<template name="model">
<listitem label="@load(each.name)" />
</template>
</listbox>