如何创建的ArrayList（ArrayList的＆LT;整数GT;）从阵列中的Java（INT []） [英] How to create ArrayList (ArrayList<Integer>) from array (int[]) in Java

问题描述

我已经看到了问题：如何创建的ArrayList（ArrayList的＆LT; T＆GT;从数组）（T []）

然而，当我尝试用以下code，它的解决方案，它在所有的情况下，不是那么回事：

However when I try that solution with following code, it doesn't quite work in all the cases:

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;

public class ToArrayList {

    public static void main(String[] args) {
        // this works
        String[] elements = new String[] { "Ryan", "Julie", "Bob" };
        List<String> list = new ArrayList<String>(Arrays.asList(elements));
        System.out.println(list);

        // this works
        List<Integer> intList = null;
        intList = Arrays.asList(3, 5);
        System.out.println(intList);

        int[] intArray = new int[] { 0, 1 };
        // this doesn't work!
        intList = new ArrayList<Integer>(Arrays.asList(intArray));
        System.out.println(intList);
    }
}

我在做什么错在这里？应该不是code intList中=新的ArrayList＆LT;整数GT;（Arrays.asList（intArray））; 编译就好了

推荐答案

在问题

intList = new ArrayList<Integer>(Arrays.asList(intArray));

是 INT [] 是因为基本数组从<$ C扩展视为一个单一的对象实例$ C>对象。如果你有这工作整数[] 而不是 INT [] ，因为现在你发送的数组对象。

is that int[] is considered as a single Object instance since a primitive array extends from Object. This would work if you have Integer[] instead of int[] since now you're sending an array of Object.

Integer[] intArray = new Integer[] { 0, 1 };
//now you're sending a Object array
intList = new ArrayList<Integer>(Arrays.asList(intArray));

从您的评论：如果你想仍使用 INT [] （或其他原始类型数组）作为主要的数据，那么你需要创建一个额外的数组包装类。对于这个例子：

From your comment: if you want to still use an int[] (or another primitive type array) as main data, then you need to create an additional array with the wrapper class. For this example:

int[] intArray = new int[] { 0, 1 };
Integer[] integerArray = new Integer[intArray.length];
int i = 0;
for(int intValue : intArray) {
    integerArray[i++] = intValue;
}
intList = new ArrayList<Integer>(Arrays.asList(integerArray));

但既然你已经在使用为循环，我不介意使用一个临时包装类数组，只需直接添加项目到列表：

But since you're already using a for loop, I wouldn't mind using a temp wrapper class array, just add your items directly into the list:

int[] intArray = new int[] { 0, 1 };
intList = new ArrayList<Integer>();
for(int intValue : intArray) {
    intList.add(intValue);
}

这篇关于如何创建的ArrayList（ArrayList的＆LT;整数GT;）从阵列中的Java（INT []）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！