JDK 9 List.of(...)

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		// JDK 9      写法: List.of(...)
//		List<Point> polygon = List.of(new Point(0, 0), new Point(0, 4), new Point(4, 4), new Point(4, 0));

		// JDK 1.6 写法：使用ArrayList并手动add元素
		List<Point> polygon = new ArrayList<Point>();
		polygon.add(new Point(0, 0));
		polygon.add(new Point(0, 4));
		polygon.add(new Point(4, 4));
		polygon.add(new Point(4, 0));

html 复制代码

JDK 9 List.of(...)

JDK 1.6            boolean add(E e);

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/**
     * Appends the specified element to the end of this list (optional
     * operation).
     *
     * <p>Lists that support this operation may place limitations on what
     * elements may be added to this list.  In particular, some
     * lists will refuse to add null elements, and others will impose
     * restrictions on the type of elements that may be added.  List
     * classes should clearly specify in their documentation any restrictions
     * on what elements may be added.
     *
     * @param e element to be appended to this list
     * @return <tt>true</tt> (as specified by {@link Collection#add})
     * @throws UnsupportedOperationException if the <tt>add</tt> operation
     *         is not supported by this list
     * @throws ClassCastException if the class of the specified element
     *         prevents it from being added to this list
     * @throws NullPointerException if the specified element is null and this
     *         list does not permit null elements
     * @throws IllegalArgumentException if some property of this element
     *         prevents it from being added to this list
     */
    boolean add(E e);

没有什么为什么，一方面以前做的项目1.6 1.8 要兼容，另一方面代码习惯，明了比简洁还要重要。