为什么indexOf找不到对象? [英] Why is indexOf failing to find the object?

问题描述

我创建了一个整数列表，并试图返回特定值的索引. 数组是3,8,2,5,1,4,7,6，我想返回indexOf(3)，应该为0.

I created an integer list and am trying to return the index of a specific value. The array is 3,8,2,5,1,4,7,6 and I want to return the indexOf(3), which should be 0.

导入java.util.*后，我在Eclipse Java Scrapbook中尝试了以下操作:

I've tried the following in the Eclipse Java Scrapbook after importing java.util.*:

int[] A = {3,8,2,5,1,4,7,9};
Arrays.asList(A).indexOf(3)

我也尝试过:

int[] A = {3,8,2,5,1,4,7,6};
ArrayList<Integer> l = new ArrayList(Arrays.asList(A));
l.indexOf(3)

两个都返回-1.为什么?如何使它按预期工作?

Both are returning -1. Why? How to get this to work as expected?

推荐答案

为使其正常运行，应该为Integer[]而不是int[].

It should be Integer[] not int[] in order to make it work.

Integer[] A = {3,8,2,5,1,4,7,9};
final int i = Arrays.asList(A).indexOf(3);
System.out.println("i = " + i); // prints '0'

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