8255529: Remove unused methods from java.util.zip.ZipFile

Reviewed-by: naoto, redestad

Author: Lance Andersen

src/java.base/share/classes/java/util/zip/ZipFile.java

@@ -1335,18 +1335,6 @@ private final void checkEncoding(ZipCoder zc, byte[] a, int pos, int nlen) throw
             }
         }
 
-        private static final int hashN(byte[] a, int off, int len) {
-            int h = 1;
-            while (len-- > 0) {
-                h = 31 * h + a[off++];
-            }
-            return h;
-        }
-
-        private static final int hash_append(int hash, byte b) {
-            return hash * 31 + b;
-        }
-
         private static class End {
             int  centot;     // 4 bytes
             long cenlen;     // 4 bytes