List.remove()的两个重载方法

最新推荐文章于 2022-12-14 13:40:29 发布

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本文介绍Java编程中使用注解处理器移除特定ID的方法。通过示例代码讲解如何遍历类的所有方法并移除带有特定注解的元素。探讨了List对象中两种remove方法的区别及其正确使用方式。

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Java编程思想20章的一个例子，20.2编写注解处理器，在list<Interger> useCases中移除注解中出现了的id（int）:

    public static void trackUseCases(List<Integer> useCases, Class<?> cl) {
        for(Method method : cl.getDeclaredMethods() ) {
            UseCase uc = method.getAnnotation(UseCase.class);
            if( uc!=null ) {
                System.out.println("Found Use Case: " + uc.id() + " " + uc.description());
//  //              useCases.remove(uc.id());     //IndexOutOfBoundsException
                useCases.remove(new Integer(uc.id()));
//或者           useCases.remove(useCases.indexOf(uc.id()));
            }
        }

        for( int i : useCases ) {
            System.out.println("Warning: Missing use case-" + i);
        }
    }

开始就写了第一种方式，结果就抛异常了，看看源码：

List对象重载了两个remove方法，1、remove(int index), 2、 remove(Object o)。

/**
     * Removes the element at the specified position in this list (optional
     * operation).  Shifts any subsequent elements to the left (subtracts one
     * from their indices).  Returns the element that was removed from the
     * list.
     *
     * @param index the index of the element to be removed
     * @return the element previously at the specified position
     * @throws UnsupportedOperationException if the <tt>remove</tt> operation
     *         is not supported by this list
     * @throws IndexOutOfBoundsException if the index is out of range
     *         (<tt>index < 0 || index >= size()</tt>)
     */
    E remove(int index);

/**
     * Removes the first occurrence of the specified element from this list,
     * if it is present (optional operation).  If this list does not contain
     * the element, it is unchanged.  More formally, removes the element with
     * the lowest index <tt>i</tt> such that
     * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>
     * (if such an element exists).  Returns <tt>true</tt> if this list
     * contained the specified element (or equivalently, if this list changed
     * as a result of the call).
     *
     * @param o element to be removed from this list, if present
     * @return <tt>true</tt> if this list contained the specified element
     * @throws ClassCastException if the type of the specified element
     *         is incompatible with this list
     * (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException if the specified element is null and this
     *         list does not permit null elements
     * (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws UnsupportedOperationException if the <tt>remove</tt> operation
     *         is not supported by this list
     */
    boolean remove(Object o);