Merge pull request #4238 from StefanSpieker/spotbugs_number_ctor

Spotbugs: Replaced inefficient Number constructor with static valueOf

core/src/main/java/hudson/tasks/BatchFile.java

@@ -67,7 +67,7 @@ public class BatchFile extends CommandInterpreter {
 
     @CheckForNull
     public final Integer getUnstableReturn() {
-        return new Integer(0).equals(unstableReturn) ? null : unstableReturn;
+        return Integer.valueOf(0).equals(unstableReturn) ? null : unstableReturn;
     }
 
     @DataBoundSetter

core/src/main/java/hudson/tasks/Shell.java

@@ -106,7 +106,7 @@ public class Shell extends CommandInterpreter {
 
     @CheckForNull
     public final Integer getUnstableReturn() {
-        return new Integer(0).equals(unstableReturn) ? null : unstableReturn;
+        return Integer.valueOf(0).equals(unstableReturn) ? null : unstableReturn;
     }
 
     @DataBoundSetter

core/src/main/java/hudson/widgets/HistoryWidget.java

@@ -285,7 +285,7 @@ public class HistoryWidget<O extends ModelObject,T> extends Widget {
             return null;
         }
         try {
-            return new Long(paramVal);
+            return Long.valueOf(paramVal);
         } catch (NumberFormatException nfe) {
             return null;
         }