src/java.base/share/classes/java/util/ServiceLoader.java

*** 1005,1024 ****
      private final class LazyClassPathLookupIterator<T>
          implements Iterator<Provider<T>>
      {
          static final String PREFIX = "META-INF/services/";
  
          Enumeration<URL> configs;
          Iterator<String> pending;
          Class<?> nextClass;
          String nextErrorMessage;  // when hasNext fails with CNFE
  
          LazyClassPathLookupIterator() { }
  
          /**
           * Parse a single line from the given configuration file, adding the
!          * name on the line to the names list.
           */
          private int parseLine(URL u, BufferedReader r, int lc, Set<String> names)
              throws IOException
          {
              String ln = r.readLine();
--- 1005,1025 ----
      private final class LazyClassPathLookupIterator<T>
          implements Iterator<Provider<T>>
      {
          static final String PREFIX = "META-INF/services/";
  
+         Set<String> providerNames = new HashSet<>();  // to avoid duplicates
          Enumeration<URL> configs;
          Iterator<String> pending;
          Class<?> nextClass;
          String nextErrorMessage;  // when hasNext fails with CNFE
  
          LazyClassPathLookupIterator() { }
  
          /**
           * Parse a single line from the given configuration file, adding the
!          * name on the line to set of names if not already seen.
           */
          private int parseLine(URL u, BufferedReader r, int lc, Set<String> names)
              throws IOException
          {
              String ln = r.readLine();
*** 1039,1050 ****
--- 1040,1053 ----
                  for (int i = start; i < n; i += Character.charCount(cp)) {
                      cp = ln.codePointAt(i);
                      if (!Character.isJavaIdentifierPart(cp) && (cp != '.'))
                          fail(service, u, lc, "Illegal provider-class name: " + ln);
                  }
+                 if (providerNames.add(ln)) {
                      names.add(ln);
                  }
+             }
              return lc + 1;
          }
  
          /**
           * Parse the content of the given URL as a provider-configuration file.
*** 1070,1080 ****
          private boolean hasNextService() {
              if (nextClass != null || nextErrorMessage != null) {
                  return true;
              }
  
!             Class<?> clazz = null;
              do {
                  if (configs == null) {
                      try {
                          String fullName = PREFIX + service.getName();
                          if (loader == null) {
--- 1073,1083 ----
          private boolean hasNextService() {
              if (nextClass != null || nextErrorMessage != null) {
                  return true;
              }
  
!             Class<?> clazz;
              do {
                  if (configs == null) {
                      try {
                          String fullName = PREFIX + service.getName();
                          if (loader == null) {