Do not disable the security manager on Java 17 VMs and newer as it is…

… deprecated for removal.

This fixes spotbugs#1579.

spotbugs/src/main/java/edu/umd/cs/findbugs/PluginLoader.java

@@ -58,6 +58,7 @@
 import javax.annotation.Nullable;
 import javax.annotation.WillClose;
 
+import edu.umd.cs.findbugs.util.SecurityManagerHandler;
 import org.dom4j.Document;
 import org.dom4j.DocumentException;
 import org.dom4j.Element;
@@ -1472,7 +1473,7 @@ static synchronized void loadInitialPlugins() {
             // Thread.currentThread().getContextClassLoader().getResource("my.java.policy");
             // Policy.getPolicy().refresh();
             try {
-                System.setSecurityManager(null);
+                SecurityManagerHandler.disableSecurityManager();
             } catch (Throwable e) {
                 assert true; // keep going
             }

spotbugs/src/main/java/edu/umd/cs/findbugs/util/SecurityManagerHandler.java

@@ -0,0 +1,59 @@
+package edu.umd.cs.findbugs.util;
+
+/**
+ * Since Java 17, the security manager is deprecated for removal and invoking related methods
+ * causes a warning to be printed to the console. This intermediate disables use security
+ * manager-related APIs on Java 17 or later, unless using the security manager is explicitly
+ * configured by setting the <i>edu.umd.cs.findbugs.securityManagerDisabled</i> property.
+ */
+public class SecurityManagerHandler {
+
+    /**
+     * Determines if the security manager is used by SpotBugs.
+     */
+    public static boolean SECURITY_MANAGER_DISABLED;
+
+    static {
+        boolean securityManagerDisabled;
+        try {
+            String property = System.getProperty("edu.umd.cs.findbugs.securityManagerDisabled");
+            if (property != null) {
+                securityManagerDisabled = Boolean.parseBoolean(property);
+            } else {
+                String version = System.getProperty("java.version");
+                if (version.startsWith("1.")) {
+                    version = version.substring(2, 3);
+                } else {
+                    int index = version.indexOf(".");
+                    if (index != -1) {
+                        version = version.substring(0, index);
+                    }
+                }
+                securityManagerDisabled = Integer.parseInt(version) > 16;
+            }
+        } catch (Throwable ignored) {
+            securityManagerDisabled = false;
+        }
+        SECURITY_MANAGER_DISABLED = securityManagerDisabled;
+    }
+
+    /**
+     * Disables the security manager by setting {@link System#setSecurityManager(SecurityManager)}
+     * to {@code null}.
+     */
+    public static void disableSecurityManager() {
+        if (SECURITY_MANAGER_DISABLED) {
+            return;
+        }
+        doDisableSecurityManager();
+    }
+
+    /**
+     * This method is a safeguard for running this library on a JVM that might no longer include
+     * the security manager API after removal. As the JVM verifies methods lazily, and since this
+     * method will never be invoked, validation of this method with a missing type can never fail.
+     */
+    private static void doDisableSecurityManager() {
+        System.setSecurityManager(null);
+    }
+}