Remove usage of enumerations

Author: kumargu

libs/agent-sm/agent-policy/src/main/java/org/opensearch/secure_sm/policy/GrantEntry.java

@@ -8,9 +8,8 @@
 package org.opensearch.secure_sm.policy;
 
 import java.io.PrintWriter;
-import java.util.Collections;
-import java.util.Enumeration;
 import java.util.LinkedList;
+import java.util.List;
 
 public class GrantEntry {
     public String codeBase;
@@ -20,8 +19,8 @@ public void add(PermissionEntry entry) {
         permissionEntries.add(entry);
     }
 
-    public Enumeration<PermissionEntry> permissionElements() {
-        return Collections.enumeration(permissionEntries);
+    public List<PermissionEntry> permissionElements() {
+        return permissionEntries;
     }
 
     public void write(PrintWriter out) {

libs/agent-sm/agent-policy/src/main/java/org/opensearch/secure_sm/policy/PolicyFile.java

@@ -29,7 +29,6 @@
 import java.security.SecurityPermission;
 import java.security.cert.Certificate;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.Enumeration;
 import java.util.List;
 import java.util.Optional;
@@ -77,7 +76,7 @@ private void init(URL policy, PolicyInfo newInfo) throws PolicyInitializationExc
             PolicyParser policyParser = new PolicyParser();
             policyParser.read(reader);
 
-            for (GrantEntry grantEntry : Collections.list(policyParser.grantElements())) {
+            for (GrantEntry grantEntry : policyParser.grantElements()) {
                 addGrantEntry(grantEntry, newInfo);
             }
 
@@ -113,24 +112,21 @@ private void addGrantEntry(GrantEntry grantEntry, PolicyInfo newInfo) throws Pol
         }
 
         PolicyEntry entry = new PolicyEntry(codesource);
-        Enumeration<PermissionEntry> enum_ = grantEntry.permissionElements();
-        while (enum_.hasMoreElements()) {
-            PermissionEntry pe = enum_.nextElement();
+        List<PermissionEntry> permissionList = grantEntry.permissionElements();
+        for (PermissionEntry pe : permissionList) {
             expandPermissionName(pe);
             try {
                 Optional<Permission> perm = getInstance(pe.permission, pe.name, pe.action);
                 if (perm.isPresent()) {
                     entry.add(perm.get());
                 }
             } catch (ClassNotFoundException e) {
-
                 // these were mostly custom permission classes added for security
                 // manager. Since security manager is deprecated, we can skip these
                 // permissions classes.
                 if (PERM_CLASSES_TO_SKIP.contains(pe.permission)) {
                     continue; // skip this permission
                 }
-
                 throw new PolicyInitializationException("Permission class not found: " + pe.permission, e);
             }
         }

libs/agent-sm/agent-policy/src/main/java/org/opensearch/secure_sm/policy/PolicyParser.java

@@ -15,7 +15,8 @@
 import java.io.IOException;
 import java.io.Reader;
 import java.io.StreamTokenizer;
-import java.util.Enumeration;
+import java.util.Collections;
+import java.util.List;
 import java.util.Optional;
 import java.util.Vector;
 
@@ -187,8 +188,8 @@ public void addGrantEntry(GrantEntry grantEntry) {
         grantEntries.addElement(grantEntry);
     }
 
-    public Enumeration<GrantEntry> grantElements() {
-        return grantEntries.elements();
+    public List<GrantEntry> grantElements() {
+        return Collections.unmodifiableList(grantEntries);
     }
 
     public static class ParsingException extends Exception {