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/*******************************************************************************
* Copyright (c) Contributors to the Eclipse Foundation
*
* 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.
*
* SPDX-License-Identifier: Apache-2.0
*******************************************************************************/
package org.osgi.util.function;
import static java.util.Objects.requireNonNull;
import org.osgi.annotation.versioning.ConsumerType;
/**
* A function that produces a result.
*
* This is a functional interface and can be used as the assignment target for a
* lambda expression or method reference.
*
* @param The type of the function output.
* @ThreadSafe
* @author $Id: ff7dbe51a4cadfb8e4088620586584a150beb9b8 $
*/
@ConsumerType
@FunctionalInterface
public interface Supplier {
/**
* Returns a value.
*
* @return The output of this function.
* @throws Exception An exception thrown by the method.
*/
T get() throws Exception;
/**
* Returns a {@code java.util.function.Supplier} which wraps the specified
* {@code Supplier} and throws any thrown exceptions.
*
* The returned {@code java.util.function.Supplier} will throw any exception
* thrown by the wrapped {@code Supplier}.
*
* @param The type of the function output.
* @param wrapped The {@code Supplier} to wrap. Must not be {@code null}.
* @return A {@code java.util.function.Supplier} which wraps the specified
* {@code Supplier}.
*/
static java.util.function.Supplier asJavaSupplier(
Supplier wrapped) {
requireNonNull(wrapped);
return () -> {
try {
return wrapped.get();
} catch (Exception e) {
throw Exceptions.throwUnchecked(e);
}
};
}
/**
* Returns a {@code java.util.function.Supplier} which wraps the specified
* {@code Supplier} and the specified value.
*
* If the the specified {@code Supplier} throws an {@code Exception}, the
* the specified value is returned.
*
* @param The type of the function output.
* @param wrapped The {@code Supplier} to wrap. Must not be {@code null}.
* @param orElse The value to return if the specified {@code Supplier}
* throws an {@code Exception}.
* @return A {@code java.util.function.Supplier} which wraps the specified
* {@code Supplier} and the specified value.
*/
static java.util.function.Supplier asJavaSupplierOrElse(
Supplier wrapped, T orElse) {
requireNonNull(wrapped);
return () -> {
try {
return wrapped.get();
} catch (Exception e) {
return orElse;
}
};
}
/**
* Returns a {@code java.util.function.Supplier} which wraps the specified
* {@code Supplier} and the specified {@code java.util.function.Supplier}.
*
* If the the specified {@code Supplier} throws an {@code Exception}, the
* value returned by the specified {@code java.util.function.Supplier} is
* returned.
*
* @param The type of the function output.
* @param wrapped The {@code Supplier} to wrap. Must not be {@code null}.
* @param orElseGet The {@code java.util.function.Supplier} to call for a
* return value if the specified {@code Supplier} throws an
* {@code Exception}.
* @return A {@code java.util.function.Supplier} which wraps the specified
* {@code Supplier} and the specified
* {@code java.util.function.Supplier}.
*/
static java.util.function.Supplier asJavaSupplierOrElseGet(
Supplier wrapped,
java.util.function.Supplier< ? extends T> orElseGet) {
requireNonNull(wrapped);
return () -> {
try {
return wrapped.get();
} catch (Exception e) {
return orElseGet.get();
}
};
}
/**
* Returns a {@code Supplier} which wraps the specified
* {@code java.util.function.Supplier}.
*
* @param The type of the function output.
* @param wrapped The {@code java.util.function.Supplier} to wrap. Must not
* be {@code null}.
* @return A {@code Supplier} which wraps the specified
* {@code java.util.Supplier.Function}.
*/
static Supplier asSupplier(java.util.function.Supplier wrapped) {
requireNonNull(wrapped);
return wrapped::get;
}
}