jdk/test/jdk/java/lang/reflect/Field/mutateFinals/jar/ExecutableJarTestHelper.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.invoke.MethodHandles;

public class ExecutableJarTestHelper {

    /**
     * The argument is a list of names of no-arg static methods in this class to invoke.
     * The names are separated with a '+'.
     */
    public static void main(String[] args) throws Exception {
        String[] methodNames = args.length > 0 ? args[0].split("\\+") : new String[0];
        for (String methodName : methodNames) {
            Method m = ExecutableJarTestHelper.class.getDeclaredMethod(methodName);
            m.invoke(null);
        }
    }

    /**
     * Uses Field.set to mutate a final field.
     */
    static void testFieldSetInt() throws Exception {
        class C {
            final int value;
            C(int value) {
                this.value = value;
            }
        }
        Field f = C.class.getDeclaredField("value");
        f.setAccessible(true);
        var obj = new C(100);
        f.setInt(obj, 200);
        if (obj.value != 200) {
            throw new RuntimeException("Unexpected value: " + obj.value);
        }
    }

    /**
     * Uses Lookup.unreflectSetter to get a method handle to set a final field.
     */
    static void testUnreflectSetter() throws Throwable {
        class C {
            final int value;
            C(int value) {
                this.value = value;
            }
        }
        Field f = C.class.getDeclaredField("value");
        f.setAccessible(true);
        var obj = new C(100);
        MethodHandles.lookup().unreflectSetter(f).invoke(obj, 200);
        if (obj.value != 200) {
            throw new RuntimeException("Unexpected value: " + obj.value);
        }
    }

    /**
     * Uses Field.set to mutate a final field of a class in a named module.
     */
    static void testFieldInNamedModule() throws Exception {
        Class<?> c = Class.forName("p.C");
        if (!c.getModule().isNamed()) {
            throw new RuntimeException(c + " is not in a named module");
        }
        Object obj = c.getDeclaredConstructor(int.class).newInstance(100);
        Field f = c.getDeclaredField("value");
        f.setAccessible(true);
        f.setInt(obj, 200);
        int newValue = f.getInt(obj);
        if (newValue != 200) {
            throw new RuntimeException("Unexpected value: " + newValue);
        }
    }
}