fix code

hutool-core/src/main/java/cn/hutool/core/lang/Singleton.java

@@ -52,7 +52,16 @@ public final class Singleton {
 	 */
 	@SuppressWarnings("unchecked")
 	public static <T> T get(final String key, final Func0<T> supplier) {
-		return (T) POOL.computeIfAbsent(key, (k)-> supplier.callWithRuntimeException());
+		//return (T) POOL.computeIfAbsent(key, (k)-> supplier.callWithRuntimeException());
+		// issues#2349
+		// ConcurrentHashMap.computeIfAbsent在某些情况下会导致死循环问题，此处采用Dubbo的解决方案
+
+		Object value = POOL.get(key);
+		if(null == value){
+			POOL.putIfAbsent(key, supplier.callWithRuntimeException());
+			value = POOL.get(key);
+		}
+		return (T) value;
 	}
 
 	/**

hutool-core/src/main/java/cn/hutool/core/map/ReferenceConcurrentMap.java

@@ -1,7 +1,6 @@
 package cn.hutool.core.map;
 
 import cn.hutool.core.collection.CollUtil;
-import cn.hutool.core.lang.func.Func0;
 import cn.hutool.core.util.ObjUtil;
 import cn.hutool.core.util.ReferenceUtil;
 
@@ -143,17 +142,6 @@ public class ReferenceConcurrentMap<K, V> implements ConcurrentMap<K, V>, Iterab
 		return this.raw.computeIfPresent(ofKey(key, this.lastQueue), (kWeakKey, value) -> remappingFunction.apply(key, value));
 	}
 
-	/**
-	 * 从缓存中获得对象，当对象不在缓存中或已经过期返回Func0回调产生的对象
-	 *
-	 * @param key      键
-	 * @param supplier 如果不存在回调方法，用于生产值对象
-	 * @return 值对象
-	 */
-	public V computeIfAbsent(final K key, final Func0<? extends V> supplier) {
-		return computeIfAbsent(key, (keyParam) -> supplier.callWithRuntimeException());
-	}
-
 	@SuppressWarnings("unchecked")
 	@Override
 	public V remove(final Object key) {

hutool-core/src/main/java/cn/hutool/core/reflect/ConstructorUtil.java

@@ -64,7 +64,7 @@ public class ConstructorUtil {
 	@SuppressWarnings("unchecked")
 	public static <T> Constructor<T>[] getConstructors(final Class<T> beanClass) throws SecurityException {
 		Assert.notNull(beanClass);
-		return (Constructor<T>[]) CONSTRUCTORS_CACHE.computeIfAbsent(beanClass, () -> getConstructorsDirectly(beanClass));
+		return (Constructor<T>[]) CONSTRUCTORS_CACHE.computeIfAbsent(beanClass, (key) -> getConstructorsDirectly(beanClass));
 	}
 
 	/**

hutool-core/src/main/java/cn/hutool/core/reflect/FieldUtil.java

@@ -116,7 +116,7 @@ public class FieldUtil {
 	 */
 	public static Field[] getFields(final Class<?> beanClass) throws SecurityException {
 		Assert.notNull(beanClass);
-		return FIELDS_CACHE.computeIfAbsent(beanClass, () -> getFieldsDirectly(beanClass, true));
+		return FIELDS_CACHE.computeIfAbsent(beanClass, (key) -> getFieldsDirectly(beanClass, true));
 	}
 
 

hutool-core/src/main/java/cn/hutool/core/reflect/MethodUtil.java

@@ -320,7 +320,7 @@ public class MethodUtil {
 	public static Method[] getMethods(final Class<?> beanClass) throws SecurityException {
 		Assert.notNull(beanClass);
 		return METHODS_CACHE.computeIfAbsent(beanClass,
-				() -> getMethodsDirectly(beanClass, true, true));
+				(key) -> getMethodsDirectly(beanClass, true, true));
 	}
 
 	/**

hutool-core/src/main/java/cn/hutool/core/util/ScriptUtil.java

@@ -30,7 +30,7 @@ public class ScriptUtil {
 	 * @return {@link ScriptEngine} 实例
 	 */
 	public static ScriptEngine getScript(final String nameOrExtOrMime) {
-		return CACHE.computeIfAbsent(nameOrExtOrMime, () -> createScript(nameOrExtOrMime));
+		return CACHE.computeIfAbsent(nameOrExtOrMime, (key) -> createScript(nameOrExtOrMime));
 	}
 
 	/**

hutool-extra/src/main/java/cn/hutool/extra/cglib/BeanCopierCache.java

@@ -43,7 +43,7 @@ public enum BeanCopierCache {
 	 */
 	public BeanCopier get(final Class<?> srcClass, final Class<?> targetClass, final boolean useConverter) {
 		final String key = genKey(srcClass, targetClass, useConverter);
-		return cache.computeIfAbsent(key, () -> BeanCopier.create(srcClass, targetClass, useConverter));
+		return cache.computeIfAbsent(key, (k) -> BeanCopier.create(srcClass, targetClass, useConverter));
 	}
 
 	/**