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Resilience4j is a lightweight, easy-to-use fault tolerance library designed for Java8 and functional programming

There is a newer version: 2.2.0

/*
 *
 *  Copyright 2020: Robert Winkler
 *
 *  Licensed 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 io.github.resilience4j.core;

import java.lang.reflect.Constructor;
import java.util.Arrays;
import java.util.Objects;
import java.util.function.Predicate;

public final class ClassUtils {

    private static final String INSTANTIATION_ERROR_PREFIX = "Unable to create instance of class: ";

    private ClassUtils() {
        // utils
    }

    public static  Predicate instantiatePredicateClass(Class> clazz) {
        try {
            Constructor> c = clazz.getConstructor();
            if (c != null) {
                return c.newInstance();
            } else {
                throw new InstantiationException(INSTANTIATION_ERROR_PREFIX + clazz.getName());
            }
        } catch (Exception e) {
            throw new InstantiationException(INSTANTIATION_ERROR_PREFIX + clazz.getName(), e);
        }
    }

    public static  T instantiateClassDefConstructor(Class clazz) {
        //if constructor present then it should have a no arg constructor
        //if not present then default constructor is already their
        Objects.requireNonNull(clazz, "class to instantiate should not be null");
        if (clazz.getConstructors().length > 0
            && Arrays.stream(clazz.getConstructors()).noneMatch(c -> c.getParameterCount() == 0)) {
            throw new InstantiationException(
                "Default constructor is required to create instance of public class: " + clazz
                    .getName());
        }
        try {
            return clazz.getConstructor().newInstance();
        } catch (Exception e) {
            throw new InstantiationException(INSTANTIATION_ERROR_PREFIX + clazz.getName(), e);
        }
    }
}