diff --git a/core/src/main/java/hudson/Main.java b/core/src/main/java/hudson/Main.java
index 55ee2fb9f0..14ae9ee38f 100644
--- a/core/src/main/java/hudson/Main.java
+++ b/core/src/main/java/hudson/Main.java
@@ -42,6 +42,7 @@ import java.net.HttpRetryException;
 import java.net.HttpURLConnection;
 import java.net.URL;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.nio.charset.Charset;
 
@@ -153,8 +154,7 @@ public class Main {
                 long start = System.currentTimeMillis();
 
                 List<String> cmd = new ArrayList<>();
-                for( int i=1; i<args.length; i++ )
-                    cmd.add(args[i]);
+                cmd.addAll(Arrays.asList(args).subList(1, args.length));
                 Proc proc = new Proc.LocalProc(cmd.toArray(new String[0]),(String[])null,System.in,
                     new DualOutputStream(System.out,new EncodingStream(os)));
 
diff --git a/core/src/main/java/hudson/model/AperiodicWork.java b/core/src/main/java/hudson/model/AperiodicWork.java
index 3c5385c077..dad7bbe573 100644
--- a/core/src/main/java/hudson/model/AperiodicWork.java
+++ b/core/src/main/java/hudson/model/AperiodicWork.java
@@ -126,9 +126,7 @@ public abstract class AperiodicWork extends SafeTimerTask implements ExtensionPo
         private final Set<AperiodicWork> registered = new HashSet<>();
 
         AperiodicWorkExtensionListListener(ExtensionList<AperiodicWork> initiallyRegistered) {
-            for (AperiodicWork p : initiallyRegistered) {
-                registered.add(p);
-            }
+            registered.addAll(initiallyRegistered);
         }
 
         @Override
diff --git a/core/src/main/java/hudson/model/PeriodicWork.java b/core/src/main/java/hudson/model/PeriodicWork.java
index 1079553551..b085a7bc41 100644
--- a/core/src/main/java/hudson/model/PeriodicWork.java
+++ b/core/src/main/java/hudson/model/PeriodicWork.java
@@ -129,9 +129,7 @@ public abstract class PeriodicWork extends SafeTimerTask implements ExtensionPoi
         private final Set<PeriodicWork> registered = new HashSet<>();
 
         PeriodicWorkExtensionListListener(ExtensionList<PeriodicWork> initiallyRegistered) {
-            for (PeriodicWork p : initiallyRegistered) {
-                registered.add(p);
-            }
+            registered.addAll(initiallyRegistered);
         }
 
         @Override
diff --git a/core/src/main/java/jenkins/model/lazy/BuildReferenceMapAdapter.java b/core/src/main/java/jenkins/model/lazy/BuildReferenceMapAdapter.java
index 8c2cd0167e..9ae3dce28b 100644
--- a/core/src/main/java/jenkins/model/lazy/BuildReferenceMapAdapter.java
+++ b/core/src/main/java/jenkins/model/lazy/BuildReferenceMapAdapter.java
@@ -170,8 +170,7 @@ class BuildReferenceMapAdapter<R> implements SortedMap<Integer,R> {
 
         public Object[] toArray() {
             List<Object> list = new ArrayList<>();
-            for (R r : this)
-                list.add(r);
+            list.addAll(this);
             return list.toArray();
         }
 
@@ -275,8 +274,7 @@ class BuildReferenceMapAdapter<R> implements SortedMap<Integer,R> {
 
         public Object[] toArray() {
             List<Object> list = new ArrayList<>();
-            for (Entry<Integer, R> r : this)
-                list.add(r);
+            list.addAll(this);
             return list.toArray();
         }