diff --git a/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/prim/Prim.java b/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/prim/Prim.java
index ec97e34341..365dca6b62 100644
--- a/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/prim/Prim.java
+++ b/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/prim/Prim.java
@@ -1,77 +1,73 @@
-package com.baeldung.algorithms.prim;
-
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
-
-import org.apache.commons.math3.util.Pair;
-
-public class Prim {
-
-    private List<Vertex> graph;
-
-    public Prim(List<Vertex> graph) {
-        this.graph = graph;
-    }
-
-    public void run() {
-        if (graph.size() > 0) {
-            graph.get(0)
-                .setVisited(true);
-        }
-        while (isDisconnected()) {
-            Edge nextMinimum = new Edge(Integer.MAX_VALUE);
-            Vertex nextVertex = graph.get(0);
-            for (Vertex vertex : graph) {
-                if (vertex.isVisited()) {
-                    Pair<Vertex, Edge> candidate = vertex.nextMinimum();
-                    if (candidate.getValue()
-                        .getWeight() < nextMinimum.getWeight()) {
-                        nextMinimum = candidate.getValue();
-                        nextVertex = candidate.getKey();
-                    }
-                }
-            }
-            nextMinimum.setIncluded(true);
-            nextVertex.setVisited(true);
-        }
-    }
-
-    private boolean isDisconnected() {
-        for (Vertex vertex : graph) {
-            if (!vertex.isVisited()) {
-                return true;
-            }
-        }
-        return false;
-    }
-
-    public String originalGraphToString() {
-        StringBuilder sb = new StringBuilder();
-        for (Vertex vertex : graph) {
-            sb.append(vertex.originalToString());
-        }
-        return sb.toString();
-    }
-
-    public void resetPrintHistory() {
-        for (Vertex vertex : graph) {
-            Iterator it = vertex.getEdges()
-                .entrySet()
-                .iterator();
-            while (it.hasNext()) {
-                Map.Entry pair = (Map.Entry) it.next();
-                ((Edge) pair.getValue()).setPrinted(false);
-            }
-        }
-    }
-
-    public String minimumSpanningTreeToString() {
-        StringBuilder sb = new StringBuilder();
-        for (Vertex vertex : graph) {
-            sb.append(vertex.includedToString());
-        }
-        return sb.toString();
-    }
-
-}
+package com.baeldung.algorithms.prim;
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.math3.util.Pair;
+
+public class Prim {
+
+    private List<Vertex> graph;
+
+    public Prim(List<Vertex> graph){
+        this.graph = graph;
+    }
+
+    public void run(){
+        if (graph.size() > 0){
+            graph.get(0).setVisited(true);
+        }
+        while (isDisconnected()){
+            Edge nextMinimum = new Edge(Integer.MAX_VALUE);
+            Vertex nextVertex = graph.get(0);
+            for (Vertex vertex : graph){
+                if (vertex.isVisited()){
+                    Pair<Vertex, Edge> candidate = vertex.nextMinimum();
+                    if (candidate.getValue().getWeight() < nextMinimum.getWeight()){
+                        nextMinimum = candidate.getValue();
+                        nextVertex = candidate.getKey();
+                    }
+                }
+            }
+            nextMinimum.setIncluded(true);
+            nextVertex.setVisited(true);
+        }
+    }
+
+    private boolean isDisconnected(){
+        for (Vertex vertex : graph){
+            if (!vertex.isVisited()){
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public String originalGraphToString(){
+        StringBuilder sb = new StringBuilder();
+        for (Vertex vertex : graph){
+            sb.append(vertex.originalToString());
+        }
+        return sb.toString();
+    }
+
+    public void resetPrintHistory(){
+        for (Vertex vertex : graph){
+            Iterator<Map.Entry<Vertex,Edge>> it = vertex.getEdges().entrySet().iterator();
+            while (it.hasNext()) {
+                Map.Entry<Vertex,Edge> pair = it.next();
+                pair.getValue().setPrinted(false);
+            }
+        }
+    }
+
+    public String minimumSpanningTreeToString(){
+        StringBuilder sb = new StringBuilder();
+        for (Vertex vertex : graph){
+            sb.append(vertex.includedToString());
+        }
+        return sb.toString();
+    }
+
+}
diff --git a/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/prim/Vertex.java b/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/prim/Vertex.java
index e2b7d90638..982d9331bc 100644
--- a/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/prim/Vertex.java
+++ b/algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/prim/Vertex.java
@@ -1,103 +1,106 @@
-package com.baeldung.algorithms.prim;
-
-import java.util.HashMap;
-import java.util.Iterator;
-import java.util.Map;
-
-import org.apache.commons.math3.util.Pair;
-
-public class Vertex {
-
-    private String label = null;
-    private Map<Vertex, Edge> edges = new HashMap<>();
-    private boolean isVisited = false;
-
-    public Vertex(String label) {
-        this.label = label;
-    }
-
-    public String getLabel() {
-        return label;
-    }
-
-    public void setLabel(String label) {
-        this.label = label;
-    }
-
-    public Map<Vertex, Edge> getEdges() {
-        return edges;
-    }
-
-    public void addEdge(Vertex vertex, Edge edge) {
-        this.edges.put(vertex, edge);
-    }
-
-    public boolean isVisited() {
-        return isVisited;
-    }
-
-    public void setVisited(boolean visited) {
-        isVisited = visited;
-    }
-
-    public Pair<Vertex, Edge> nextMinimum() {
-        Edge nextMinimum = new Edge(Integer.MAX_VALUE);
-        Vertex nextVertex = this;
-        Iterator it = edges.entrySet()
-            .iterator();
-        while (it.hasNext()) {
-            Map.Entry pair = (Map.Entry) it.next();
-            if (!((Vertex) pair.getKey()).isVisited()) {
-                if (!((Edge) pair.getValue()).isIncluded()) {
-                    if (((Edge) pair.getValue()).getWeight() < nextMinimum.getWeight()) {
-                        nextMinimum = (Edge) pair.getValue();
-                        nextVertex = (Vertex) pair.getKey();
-                    }
-                }
-            }
-        }
-        return new Pair<>(nextVertex, nextMinimum);
-    }
-
-    public String originalToString() {
-        StringBuilder sb = new StringBuilder();
-        Iterator it = edges.entrySet()
-            .iterator();
-        while (it.hasNext()) {
-            Map.Entry pair = (Map.Entry) it.next();
-            if (!((Edge) pair.getValue()).isPrinted()) {
-                sb.append(getLabel());
-                sb.append(" --- ");
-                sb.append(((Edge) pair.getValue()).getWeight());
-                sb.append(" --- ");
-                sb.append(((Vertex) pair.getKey()).getLabel());
-                sb.append("\n");
-                ((Edge) pair.getValue()).setPrinted(true);
-            }
-        }
-        return sb.toString();
-    }
-
-    public String includedToString() {
-        StringBuilder sb = new StringBuilder();
-        if (isVisited()) {
-            Iterator it = edges.entrySet()
-                .iterator();
-            while (it.hasNext()) {
-                Map.Entry pair = (Map.Entry) it.next();
-                if (((Edge) pair.getValue()).isIncluded()) {
-                    if (!((Edge) pair.getValue()).isPrinted()) {
-                        sb.append(getLabel());
-                        sb.append(" --- ");
-                        sb.append(((Edge) pair.getValue()).getWeight());
-                        sb.append(" --- ");
-                        sb.append(((Vertex) pair.getKey()).getLabel());
-                        sb.append("\n");
-                        ((Edge) pair.getValue()).setPrinted(true);
-                    }
-                }
-            }
-        }
-        return sb.toString();
-    }
-}
+package com.baeldung.algorithms.prim;
+
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+
+import org.apache.commons.math3.util.Pair;
+
+public class Vertex {
+
+    private String label = null;
+    private Map<Vertex, Edge> edges = new HashMap<>();
+    private boolean isVisited = false;
+
+    public Vertex(String label){
+        this.label = label;
+    }
+
+    public String getLabel() {
+        return label;
+    }
+
+    public void setLabel(String label) {
+        this.label = label;
+    }
+
+    public Map<Vertex, Edge> getEdges() {
+        return edges;
+    }
+
+    public void addEdge(Vertex vertex, Edge edge){
+        if (this.edges.containsKey(vertex)){
+            if (edge.getWeight() < this.edges.get(vertex).getWeight()){
+                this.edges.replace(vertex, edge);
+            }
+        } else {
+            this.edges.put(vertex, edge);
+        }
+    }
+
+    public boolean isVisited() {
+        return isVisited;
+    }
+
+    public void setVisited(boolean visited) {
+        isVisited = visited;
+    }
+
+    public Pair<Vertex, Edge> nextMinimum(){
+        Edge nextMinimum = new Edge(Integer.MAX_VALUE);
+        Vertex nextVertex = this;
+        Iterator<Map.Entry<Vertex,Edge>> it = edges.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<Vertex,Edge> pair = it.next();
+            if (!pair.getKey().isVisited()){
+                if (!pair.getValue().isIncluded()) {
+                    if (pair.getValue().getWeight() < nextMinimum.getWeight()) {
+                        nextMinimum = pair.getValue();
+                        nextVertex = pair.getKey();
+                    }
+                }
+            }
+        }
+        return new Pair<>(nextVertex, nextMinimum);
+    }
+
+    public String originalToString(){
+        StringBuilder sb = new StringBuilder();
+        Iterator<Map.Entry<Vertex,Edge>> it = edges.entrySet().iterator();
+        while (it.hasNext()) {
+            Map.Entry<Vertex,Edge> pair = it.next();
+            if (!pair.getValue().isPrinted()) {
+                sb.append(getLabel());
+                sb.append(" --- ");
+                sb.append(pair.getValue().getWeight());
+                sb.append(" --- ");
+                sb.append(pair.getKey().getLabel());
+                sb.append("\n");
+                pair.getValue().setPrinted(true);
+            }
+        }
+        return sb.toString();
+    }
+
+    public String includedToString(){
+        StringBuilder sb = new StringBuilder();
+        if (isVisited()) {
+            Iterator<Map.Entry<Vertex,Edge>> it = edges.entrySet().iterator();
+            while (it.hasNext()) {
+                Map.Entry<Vertex,Edge> pair = it.next();
+                if (pair.getValue().isIncluded()) {
+                    if (!pair.getValue().isPrinted()) {
+                        sb.append(getLabel());
+                        sb.append(" --- ");
+                        sb.append(pair.getValue().getWeight());
+                        sb.append(" --- ");
+                        sb.append(pair.getKey().getLabel());
+                        sb.append("\n");
+                        pair.getValue().setPrinted(true);
+                    }
+                }
+            }
+        }
+        return sb.toString();
+    }
+}