7113208: Incorrect javadoc on java.net.DatagramPacket.setLength()

Reviewed-by: dfuchs

src/java.base/share/classes/java/net/DatagramPacket.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1995, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1995, 2022, 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
@@ -25,6 +25,10 @@
 
 package java.net;
 
+import java.util.Objects;
+
+import jdk.internal.util.Preconditions;
+
 /**
  * This class represents a datagram packet.
  * <p>
@@ -285,12 +289,9 @@ public synchronized int getLength() {
      * @since   1.2
      */
     public synchronized void setData(byte[] buf, int offset, int length) {
-        /* this will check to see if buf is null */
-        if (length < 0 || offset < 0 ||
-            (length + offset) < 0 ||
-            ((length + offset) > buf.length)) {
-            throw new IllegalArgumentException("illegal length or offset");
-        }
+        Objects.requireNonNull(buf);
+        Preconditions.checkFromIndexSize(offset, length, buf.length,
+                Preconditions.outOfBoundsExceptionFormatter(IllegalArgumentException::new));
         this.buf = buf;
         this.length = length;
         this.bufLength = length;
@@ -394,8 +395,9 @@ public synchronized void setData(byte[] buf) {
      * Set the length for this packet. The length of the packet is
      * the number of bytes from the packet's data buffer that will be
      * sent, or the number of bytes of the packet's data buffer that
-     * will be used for receiving data. The length must be lesser or
-     * equal to the offset plus the length of the packet's buffer.
+     * will be used for receiving data. The {@code length} plus the
+     * {@link #getOffset() offset} must be lesser or equal to the
+     * length of the packet's data buffer.
      *
      * @param   length      the length to set for this packet.
      *
@@ -409,10 +411,8 @@ public synchronized void setData(byte[] buf) {
      * @since   1.1
      */
     public synchronized void setLength(int length) {
-        if ((length + offset) > buf.length || length < 0 ||
-            (length + offset) < 0) {
-            throw new IllegalArgumentException("illegal length");
-        }
+        Preconditions.checkFromIndexSize(offset, length, buf.length,
+                Preconditions.outOfBoundsExceptionFormatter(IllegalArgumentException::new));
         this.length = length;
         this.bufLength = this.length;
     }