8312089: Simplify and modernize equals, hashCode, and compareTo in java.nio and implementation code

Reviewed-by: alanb, vtewari

src/java.base/share/classes/java/nio/charset/Charset.java

@@ -954,15 +954,15 @@ public abstract class Charset
      * @return A negative integer, zero, or a positive integer as this charset
      *         is less than, equal to, or greater than the specified charset
      */
+    @Override
     public final int compareTo(Charset that) {
         return (name().compareToIgnoreCase(that.name()));
     }
 
     /**
-     * Computes a hashcode for this charset.
-     *
-     * @return  An integer hashcode
+     * {@return the hashcode for this charset}
      */
+    @Override
     public final int hashCode() {
         return name().hashCode();
     }
@@ -976,19 +976,17 @@ public abstract class Charset
      * @return  {@code true} if, and only if, this charset is equal to the
      *          given object
      */
+    @Override
     public final boolean equals(Object ob) {
-        if (!(ob instanceof Charset))
-            return false;
         if (this == ob)
             return true;
-        return name.equals(((Charset)ob).name());
+        return ob instanceof Charset other && name.equals(other.name());
     }
 
     /**
-     * Returns a string describing this charset.
-     *
-     * @return  A string describing this charset
+     * {@return a string describing this charset}
      */
+    @Override
     public final String toString() {
         return name();
     }

src/java.base/share/classes/java/nio/file/Path.java

@@ -984,6 +984,7 @@ public interface Path
      * @return  {@code true} if, and only if, the given object is a {@code Path}
      *          that is identical to this {@code Path}
      */
+    @Override
     boolean equals(Object other);
 
     /**
@@ -995,10 +996,11 @@ public interface Path
      *
      * @return  the hash-code value for this path
      */
+    @Override
     int hashCode();
 
     /**
-     * Returns the string representation of this path.
+     * {@return the string representation of this path}
      *
      * <p> If this path was created by converting a path string using the
      * {@link FileSystem#getPath getPath} method then the path string returned
@@ -1006,8 +1008,7 @@ public interface Path
      *
      * <p> The returned path string uses the default name {@link
      * FileSystem#getSeparator separator} to separate names in the path.
-     *
-     * @return  the string representation of this path
      */
+    @Override
     String toString();
 }

src/java.base/share/classes/java/nio/file/attribute/AclEntry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2007, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2007, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -357,10 +357,6 @@ public final class AclEntry {
         return true;
     }
 
-    private static int hash(int h, Object o) {
-        return h * 127 + o.hashCode();
-    }
-
     /**
      * Returns the hash-code value for this ACL entry.
      *
@@ -370,14 +366,12 @@ public final class AclEntry {
     @Override
     public int hashCode() {
         // return cached hash if available
-        if (hash != 0)
-            return hash;
-        int h = type.hashCode();
-        h = hash(h, who);
-        h = hash(h, perms);
-        h = hash(h, flags);
-        hash = h;
-        return hash;
+        int h = hash;
+        if (h == 0) {
+            h = Objects.hash(type, who, perms, flags);
+            hash = h;
+        }
+        return h;
     }
 
     /**

src/java.base/share/classes/java/nio/file/attribute/FileTime.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2009, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -291,7 +291,7 @@ public final class FileTime
      */
     @Override
     public boolean equals(Object obj) {
-        return (obj instanceof FileTime) ? compareTo((FileTime)obj) == 0 : false;
+        return obj instanceof FileTime other && compareTo(other) == 0;
     }
 
     /**