diff --git a/core/src/main/java/info/openrocket/core/optimization/services/DefaultSimulationModifierService.java b/core/src/main/java/info/openrocket/core/optimization/services/DefaultSimulationModifierService.java
index 8775059e7..e2dfd8424 100644
--- a/core/src/main/java/info/openrocket/core/optimization/services/DefaultSimulationModifierService.java
+++ b/core/src/main/java/info/openrocket/core/optimization/services/DefaultSimulationModifierService.java
@@ -107,13 +107,9 @@ public class DefaultSimulationModifierService implements SimulationModifierServi
 			Class<? extends RocketComponent> componentClass, String methodName, String autoMethod) {
 		
 		String modifierDescriptionKey = modifierNameKey + ".desc";
-		
-		List<ModifierDefinition> list = definitions.get(componentClass);
-		if (list == null) {
-			list = new ArrayList<>();
-			definitions.put(componentClass, list);
-		}
-		
+
+		List<ModifierDefinition> list = definitions.computeIfAbsent(componentClass, k -> new ArrayList<>());
+
 		ModifierDefinition definition = new ModifierDefinition(modifierNameKey, modifierDescriptionKey, unitGroup,
 				multiplier, componentClass, methodName, autoMethod);
 		list.add(definition);
diff --git a/core/src/main/java/info/openrocket/core/thrustcurve/DownloadResponse.java b/core/src/main/java/info/openrocket/core/thrustcurve/DownloadResponse.java
index 1b1c017cb..8f4762d55 100644
--- a/core/src/main/java/info/openrocket/core/thrustcurve/DownloadResponse.java
+++ b/core/src/main/java/info/openrocket/core/thrustcurve/DownloadResponse.java
@@ -12,11 +12,7 @@ public class DownloadResponse {
 	private String error = null;
 
 	public void add(MotorBurnFile mbd) {
-		List<MotorBurnFile> currentData = data.get(mbd.getMotorId());
-		if (currentData == null) {
-			currentData = new ArrayList<>();
-			data.put(mbd.getMotorId(), currentData);
-		}
+		List<MotorBurnFile> currentData = data.computeIfAbsent(mbd.getMotorId(), k -> new ArrayList<>());
 		currentData.add(mbd);
 	}
 
diff --git a/swing/src/main/java/info/openrocket/swing/gui/dialogs/ScaleDialog.java b/swing/src/main/java/info/openrocket/swing/gui/dialogs/ScaleDialog.java
index f16b302a2..c19a14985 100644
--- a/swing/src/main/java/info/openrocket/swing/gui/dialogs/ScaleDialog.java
+++ b/swing/src/main/java/info/openrocket/swing/gui/dialogs/ScaleDialog.java
@@ -205,11 +205,7 @@ public class ScaleDialog extends JDialog {
 	
 	private static void addScaler(Class<? extends RocketComponent> componentClass, String methodName, String autoMethodName,
 								  Map<Class<? extends RocketComponent>, List<Scaler>> scaler) {
-		List<Scaler> list = scaler.get(componentClass);
-		if (list == null) {
-			list = new ArrayList<>();
-			scaler.put(componentClass, list);
-		}
+		List<Scaler> list = scaler.computeIfAbsent(componentClass, k -> new ArrayList<>());
 		list.add(new GeneralScaler(componentClass, methodName, autoMethodName));
 	}
 	
diff --git a/swing/src/main/java/info/openrocket/swing/gui/dialogs/optimization/GeneralOptimizationDialog.java b/swing/src/main/java/info/openrocket/swing/gui/dialogs/optimization/GeneralOptimizationDialog.java
index 2622c0c7a..e0890c501 100644
--- a/swing/src/main/java/info/openrocket/swing/gui/dialogs/optimization/GeneralOptimizationDialog.java
+++ b/swing/src/main/java/info/openrocket/swing/gui/dialogs/optimization/GeneralOptimizationDialog.java
@@ -1017,11 +1017,7 @@ public class GeneralOptimizationDialog extends JDialog {
 		
 		for (SimulationModifier m : OptimizationServiceHelper.getSimulationModifiers(documentCopy)) {
 			Object key = m.getRelatedObject();
-			List<SimulationModifier> list = simulationModifiers.get(key);
-			if (list == null) {
-				list = new ArrayList<>();
-				simulationModifiers.put(key, list);
-			}
+			List<SimulationModifier> list = simulationModifiers.computeIfAbsent(key, k -> new ArrayList<>());
 			list.add(m);
 		}
 		
diff --git a/swing/src/main/java/info/openrocket/swing/gui/print/PrintableContext.java b/swing/src/main/java/info/openrocket/swing/gui/print/PrintableContext.java
index 899c12e92..ceb7e2e70 100644
--- a/swing/src/main/java/info/openrocket/swing/gui/print/PrintableContext.java
+++ b/swing/src/main/java/info/openrocket/swing/gui/print/PrintableContext.java
@@ -60,11 +60,7 @@ public class PrintableContext implements Comparable<PrintableContext>, Iterable<
 	 * @param thePrintable    the printable to associate with the stage
 	 */
 	public void add(final Integer theStageNumber, final OpenRocketPrintable thePrintable) {
-		Set<Integer> stages = previous.get(thePrintable);
-		if (stages == null) {
-			stages = new TreeSet<>();
-			previous.put(thePrintable, stages);
-		}
+		Set<Integer> stages = previous.computeIfAbsent(thePrintable, k -> new TreeSet<>());
 		if (theStageNumber != null) {
 			stages.add(theStageNumber);
 		}