45 lines
1.1 KiB
Java
45 lines
1.1 KiB
Java
// typeinfo/HiddenImplementation.java
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// (c)2020 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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// Sneaking around package hiding
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import typeinfo.interfacea.*;
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import typeinfo.packageaccess.*;
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import java.lang.reflect.*;
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public class HiddenImplementation {
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public static void
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main(String[] args) throws Exception {
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A a = HiddenC.makeA();
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a.f();
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System.out.println(a.getClass().getName());
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// Compile error: cannot find symbol 'C':
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/* if(a instanceof C) {
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C c = (C)a;
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c.g();
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} */
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// Oops! Reflection still allows us to call g():
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callHiddenMethod(a, "g");
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// And even less accessible methods!
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callHiddenMethod(a, "u");
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callHiddenMethod(a, "v");
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callHiddenMethod(a, "w");
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}
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static void
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callHiddenMethod(Object a, String methodName)
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throws Exception {
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Method g =
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a.getClass().getDeclaredMethod(methodName);
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g.setAccessible(true);
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g.invoke(a);
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}
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}
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/* Output:
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public C.f()
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typeinfo.packageaccess.C
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public C.g()
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package C.u()
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protected C.v()
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private C.w()
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*/
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