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  • java array to list

    背景

    想把数组转为list,使用list的判断元素是否存在的方法,结果发现一个坑,int类型的数组失败了 

    步骤

    public static void main(String[] args) {
            int[] nums = {3, 5, 1, 2, 9};
    
            System.out.println(Arrays.asList(nums).size());
    
    
        }
    
    结果为1

     这样不行,会有boxing issue

    google结果是这样

    //it is because you can't have a List of a primitive type. In other words, List<int> is not possible. You can, however, have a List<Integer>.
    
    Integer[] spam = new Integer[] { 1, 2, 3 };
    Arrays.asList(spam);

    //没有list<int> 这玩意,可以用list<Integer>

    java 8 的话可以这样:

    int[] nums = {3, 5, 1, 2, 9};
    List<Integer> list = Arrays.stream(nums).boxed().collect(Collectors.toList());

    可以参考:https://www.mkyong.com/java/java-how-to-convert-a-primitive-array-to-list/

    不太理解,有理解的话,麻烦留言解释一哈

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  • 原文地址:https://www.cnblogs.com/jwentest/p/7145649.html
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