Expose contains, remove and clear methods on ConcurrentLruCache

Closes gh-25963

spring-core/src/main/java/org/springframework/util/ConcurrentLruCache.java

@@ -105,17 +105,15 @@ public class ConcurrentLruCache<K, V> {
 			}
 			// Generate value first, to prevent size inconsistency
 			V value = this.generator.apply(key);
-			int cacheSize = this.size;
-			if (cacheSize == this.sizeLimit) {
+			if (this.size == this.sizeLimit) {
 				K leastUsed = this.queue.poll();
 				if (leastUsed != null) {
 					this.cache.remove(leastUsed);
-					cacheSize--;
 				}
 			}
 			this.queue.offer(key);
 			this.cache.put(key, value);
-			this.size = cacheSize + 1;
+			this.size = this.cache.size();
 			return value;
 		}
 		finally {
@@ -123,6 +121,50 @@ public class ConcurrentLruCache<K, V> {
 		}
 	}
 
+	/**
+	 * Determine whether the given key is present in this cache.
+	 * @param key the key to check for
+	 * @return {@code true} if the key is present,
+	 * {@code false} if there was no matching key
+	 */
+	public boolean contains(K key) {
+		return this.cache.containsKey(key);
+	}
+
+	/**
+	 * Immediately remove the given key and any associated value.
+	 * @param key the key to evict the entry for
+	 * @return {@code true} if the key was present before,
+	 * {@code false} if there was no matching key
+	 */
+	public boolean remove(K key) {
+		this.lock.writeLock().lock();
+		try {
+			boolean wasPresent = (this.cache.remove(key) != null);
+			this.queue.remove(key);
+			this.size = this.cache.size();
+			return wasPresent;
+		}
+		finally {
+			this.lock.writeLock().unlock();
+		}
+	}
+
+	/**
+	 * Immediately remove all entries from this cache.
+	 */
+	public void clear() {
+		this.lock.writeLock().lock();
+		try {
+			this.cache.clear();
+			this.queue.clear();
+			this.size = 0;
+		}
+		finally {
+			this.lock.writeLock().unlock();
+		}
+	}
+
 	/**
 	 * Return the current size of the cache.
 	 * @see #sizeLimit()

spring-core/src/test/java/org/springframework/util/ConcurrentLruCacheTests.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2002-2020 the original author or authors.
+ *
+ * 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.springframework.util;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Juergen Hoeller
+ */
+class ConcurrentLruCacheTests {
+
+	private final ConcurrentLruCache<String, String> cache = new ConcurrentLruCache<>(2, key -> key + "value");
+
+
+	@Test
+	void getAndSize() {
+		assertThat(this.cache.sizeLimit()).isEqualTo(2);
+		assertThat(this.cache.size()).isEqualTo(0);
+		assertThat(this.cache.get("k1")).isEqualTo("k1value");
+		assertThat(this.cache.size()).isEqualTo(1);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.get("k2")).isEqualTo("k2value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isTrue();
+		assertThat(this.cache.get("k3")).isEqualTo("k3value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isFalse();
+		assertThat(this.cache.contains("k2")).isTrue();
+		assertThat(this.cache.contains("k3")).isTrue();
+	}
+
+	@Test
+	void removeAndSize() {
+		assertThat(this.cache.get("k1")).isEqualTo("k1value");
+		assertThat(this.cache.get("k2")).isEqualTo("k2value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isTrue();
+		this.cache.remove("k2");
+		assertThat(this.cache.size()).isEqualTo(1);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isFalse();
+		assertThat(this.cache.get("k3")).isEqualTo("k3value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isFalse();
+		assertThat(this.cache.contains("k3")).isTrue();
+	}
+
+	@Test
+	void clearAndSize() {
+		assertThat(this.cache.get("k1")).isEqualTo("k1value");
+		assertThat(this.cache.get("k2")).isEqualTo("k2value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isTrue();
+		this.cache.clear();
+		assertThat(this.cache.size()).isEqualTo(0);
+		assertThat(this.cache.contains("k1")).isFalse();
+		assertThat(this.cache.contains("k2")).isFalse();
+		assertThat(this.cache.get("k3")).isEqualTo("k3value");
+		assertThat(this.cache.size()).isEqualTo(1);
+		assertThat(this.cache.contains("k1")).isFalse();
+		assertThat(this.cache.contains("k2")).isFalse();
+		assertThat(this.cache.contains("k3")).isTrue();
+	}
+
+}