[refactor] Java8: Replace with simple Map method call

Author: dizzzz

exist-core/src/main/java/org/exist/management/impl/JMXAgent.java

@@ -93,7 +93,8 @@ public synchronized void initDBInstance(final BrokerPool instance) {
             try {
                 addMBean(perInstanceMBean);
             } catch (final DatabaseConfigurationException e) {
-                LOG.warn("Exception while registering JMX MBean: {}, for database: {}.", perInstanceMBean.getClass().getName(), instance.getId(), e);
+                LOG.warn("Exception while registering JMX MBean: {}, for database: {}.", 
+                        perInstanceMBean.getClass().getName(), instance.getId(), e);
             }
         }
     }
@@ -116,11 +117,7 @@ public synchronized void addMBean(final PerInstanceMBean mbean) throws DatabaseC
         try {
             addMBean(mbean.getName(), mbean);
             if (mbean.getInstanceId() != null) {
-                Deque<ObjectName> stack = registeredMBeans.get(mbean.getInstanceId());
-                if (stack == null) {
-                    stack = new ArrayDeque<>();
-                    registeredMBeans.put(mbean.getInstanceId(), stack);
-                }
+                Deque<ObjectName> stack = registeredMBeans.computeIfAbsent(mbean.getInstanceId(), k -> new ArrayDeque<>());
                 stack.push(mbean.getName());
             }
             beanInstances.put(mbean.getName(), mbean);

exist-core/src/main/java/org/exist/storage/lock/LockTable.java

@@ -171,12 +171,8 @@ private void event(final LockEventType lockEventType, final long groupId, final
         switch (lockEventType) {
             case Attempt:
 
-                Entry entry = attempting.get(currentThread);
-                if (entry == null) {
-                    // happens once per thread!
-                    entry = new Entry();
-                    attempting.put(currentThread, entry);
-                }
+                // happens once per thread!
+                Entry entry = attempting.computeIfAbsent(currentThread, k -> new Entry());
 
                 entry.id = id;
                 entry.lockType = lockType;

exist-core/src/main/java/org/exist/xquery/AbstractInternalModule.java

@@ -179,11 +179,7 @@ public Iterator<QName> getGlobalVariables() {
     @Override
     public Variable declareVariable(final QName qname, final Object value) throws XPathException {
         final Sequence val = XPathUtil.javaObjectToXPath(value, null, null);
-        Variable var = mGlobalVariables.get(qname);
-        if (var == null){
-            var = new VariableImpl(qname);
-            mGlobalVariables.put(qname, var);
-        }
+        Variable var = mGlobalVariables.computeIfAbsent(qname, VariableImpl::new);
         var.setValue(val);
         return var;
     }

exist-core/src/main/java/org/exist/xquery/ExternalModuleImpl.java

@@ -188,11 +188,7 @@ public Collection<VariableDeclaration> getVariableDeclarations() {
      */
     public Variable declareVariable(QName qname, Object value) throws XPathException {
         final Sequence val = XPathUtil.javaObjectToXPath(value, mContext, null);
-        Variable var = mStaticVariables.get(qname);
-        if (var == null) {
-            var = new VariableImpl(qname);
-            mStaticVariables.put(qname, var);
-        }
+        Variable var = mStaticVariables.computeIfAbsent(qname, VariableImpl::new);
         var.setValue(val);
         return var;
     }