diff --git a/eu.heili/AndGate.java b/eu.heili/AndGate.java
index 63c0b7c..1fc995b 100644
--- a/eu.heili/AndGate.java
+++ b/eu.heili/AndGate.java
@@ -1,11 +1,11 @@
 public class AndGate extends LogicGate {
-    public AndGate(int inputnr) {
+    public AndGate(final int inputnr) {
         super(inputnr);
         if (inputnr > 8)
             throw (new TooManyInputsException());
     }
 
-    public AndGate(DigitalInput... inputvals) {
+    public AndGate(final DigitalInput... inputvals) {
         super(inputvals);
     }
 
diff --git a/eu.heili/DigitalInput.java b/eu.heili/DigitalInput.java
index 133b207..a7ff6c0 100644
--- a/eu.heili/DigitalInput.java
+++ b/eu.heili/DigitalInput.java
@@ -1,7 +1,7 @@
 public class DigitalInput {
     private boolean value = false;
 
-    public DigitalInput(boolean value) {
+    public DigitalInput(final boolean value) {
         setValue(value);
     }
 
@@ -9,11 +9,11 @@ public class DigitalInput {
         setValue(gate);
     }
 
-    public DigitalInput(int value) {
+    public DigitalInput(final int value) {
         setValue(value);
     }
 
-    public DigitalInput(char value) {
+    public DigitalInput(final char value) {
         setValue(value);
     }
 
diff --git a/eu.heili/LogicGate.java b/eu.heili/LogicGate.java
index 5f915f5..4e1f1e3 100644
--- a/eu.heili/LogicGate.java
+++ b/eu.heili/LogicGate.java
@@ -4,13 +4,13 @@ import java.util.Arrays;
 public abstract class LogicGate {
     private final ArrayList<DigitalInput> inputs = new ArrayList<>();
 
-    public LogicGate(int inputnr) {
+    public LogicGate(final int inputnr) {
         for (int i = 0; i < inputnr; i++) {
             inputs.add(new DigitalInput()); // generate new objects for new inputs
         }
     }
 
-    public LogicGate(DigitalInput... inputvals) {
+    public LogicGate(final DigitalInput... inputvals) {
         inputs.addAll(Arrays.asList(inputvals));
     }
 
@@ -21,7 +21,7 @@ public abstract class LogicGate {
      */
     public abstract boolean getOutput();
 
-    public DigitalInput getInput(int nr) {
+    public DigitalInput getInput(final int nr) {
         if (nr >= getInputNumber())
             throw (new InputOutOfBoundsException());
         return inputs.get(nr);
@@ -31,7 +31,7 @@ public abstract class LogicGate {
         return inputs.size();
     }
 
-    public void addInput(DigitalInput in) {
+    public void addInput(final DigitalInput in) {
         inputs.add(in);
     }
 }
diff --git a/eu.heili/OrGate.java b/eu.heili/OrGate.java
index f21f0a6..c3b60d5 100644
--- a/eu.heili/OrGate.java
+++ b/eu.heili/OrGate.java
@@ -1,9 +1,9 @@
 public class OrGate extends LogicGate {
-    public OrGate(int inputnr) {
+    public OrGate(final int inputnr) {
         super(inputnr);
     }
 
-    public OrGate(DigitalInput... inputvals) {
+    public OrGate(final DigitalInput... inputvals) {
         super(inputvals);
     }