org.ehrbase.util.Lazy Maven / Gradle / Ivy
/*
* Copyright (c) 2024 vitasystems GmbH.
*
* This file is part of project EHRbase
*
* 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
*
* https://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.ehrbase.util;
import java.util.function.Supplier;
/**
* Lazy property value that can be used to cache values with "expensive" calculations during first time of access.
*
* Usage:
*
* {@code
* import static org.ehrbase.util.Lazy.lazy;
*
* class MyClass {
*
* private final Supplier lazyValue = lazy(() -> "some expensive calculated value");
*
* public String getValue() {
* return lazyValue.get();
* }
* }
* }
*
* @param
*/
public final class Lazy implements Supplier {
private V value; // = null
private final Supplier supplier;
public Lazy(Supplier supplier) {
this.supplier = supplier;
}
@Override
public V get() {
if (value == null) {
value = supplier.get();
}
return value;
}
public static Supplier lazy(Supplier supplier) {
return new Lazy(supplier);
}
}