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Apache Commons Lang, a package of Java utility classes for the classes that are in java.lang's hierarchy, or are considered to be so standard as to justify existence in java.lang. The code is tested using the latest revision of the JDK for supported LTS releases: 8, 11, 17 and 21 currently. See https://github.com/apache/commons-lang/blob/master/.github/workflows/maven.yml Please ensure your build environment is up-to-date and kindly report any build issues.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3.time;

import java.lang.reflect.Method;
import java.util.Calendar;
import java.util.GregorianCalendar;

import org.apache.commons.lang3.exception.ExceptionUtils;

/**
 * Use reflection to access java 1.7 methods in Calendar.  This allows compilation with 1.6 compiler.
 */
class CalendarReflection {

    private static final Method IS_WEEK_DATE_SUPPORTED = getCalendarMethod("isWeekDateSupported");
    private static final Method GET_WEEK_YEAR = getCalendarMethod("getWeekYear");

    private static Method getCalendarMethod(String methodName, Class... argTypes) {
        try {
            Method m = Calendar.class.getMethod(methodName, argTypes);
            return m;
        } catch (Exception e) {
            return null;
        }
    }

    /**
     * Does this calendar instance support week date?
     * @param calendar The calendar instance.
     * @return false, if runtime is less than java 1.7; otherwise, the result of calendar.isWeekDateSupported().
     */
    static boolean isWeekDateSupported(Calendar calendar) {
        try {
            return IS_WEEK_DATE_SUPPORTED!=null && ((Boolean)IS_WEEK_DATE_SUPPORTED.invoke(calendar)).booleanValue();
        } catch (Exception e) {
            return ExceptionUtils.rethrow(e);
        }
    }

    /**
     * Invoke getWeekYear() method of calendar instance.
     * 

* If runtime is 1.7 or better and calendar instance support week year, * return the value from invocation of getWeekYear(). *

* If runtime is less than 1.7, and calendar is an instance of * GregorianCalendar, return an approximation of the week year. * (Approximation is good for all years after the Julian to Gregorian * cutover.) *

* Otherwise, return the calendar instance year value. * * @param calendar The calendar instance. * @return the week year or year value. */ public static int getWeekYear(Calendar calendar) { try { if (isWeekDateSupported(calendar)) { return (Integer) GET_WEEK_YEAR.invoke(calendar); } } catch (Exception e) { return ExceptionUtils. rethrow(e); } int year = calendar.get(Calendar.YEAR); if (IS_WEEK_DATE_SUPPORTED == null && calendar instanceof GregorianCalendar) { // not perfect, won't work before gregorian cutover // good enough for most business use. switch (calendar.get(Calendar.MONTH)) { case Calendar.JANUARY: if (calendar.get(Calendar.WEEK_OF_YEAR) >= 52) { --year; } break; case Calendar.DECEMBER: if (calendar.get(Calendar.WEEK_OF_YEAR) == 1) { ++year; } break; } } return year; } }





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