如何使用Array.toString()打印数组的所有非null元素 [英] How to print all non null elements of an array using Array.toString()

问题描述

所以我需要打印出一个整数数组.问题是，当用户输入要处理和排序的数字时，我不知道用户将输入多少个数字.唯一的规则是用户只能输入少于10000个数字.

So I need to print out an array of integers. The problem is that when user enters the numbers to be processed and sorted, I do not know how many numbers there will be entered by the user. The only rule to that is that user can enter only less than 10000 numbers.

因此，我制作了一个可以容纳10000个数字的数组，但是如果用户在该数组中输入的数字少于10000个，那么 Array.toString()函数将打印出所有内容，甚至包括空格.

So I made an array which can hold 10000 numbers but if user enters less than 10000 numbers into the array then Array.toString() function prints out everything, even the empty spaces.

是否有任何方法可以绕过该方法，或者是否有其他方法可以在一行中输出一个数组，以格式化输出，使其看起来像这样: [1、2、3、4、5、6]

Is there any way to bypass that or are there any other methods for outputting an array in one line that would format it the output to look like this: [1, 2, 3, 4, 5, 6]

非常感谢！

推荐答案

ArrayList< T> (对于泛型，可选地为< T> ).是一个数组，如果有更多输入可用，它会动态添加更多内存.将元素添加到此类列表的摊销成本为 O(1)，但它提供了一种方便的方式来处理输入.

An ArrayList<T> (optionally <T> for generics). Is an array that dynamically adds more memory if more input comes available. The amortized cost of adding an element to such list is O(1), but it offers a convenient way to process input.

要回答您的问题，正如@Mureinik已经回答的那样，您可以使用 ArrayList.toString()将列表转换为文本表示形式.

To answer your question, as @Mureinik already answered you then can use ArrayList.toString() to convert the list to a textual representation.

要回答您的真实问题，您可以执行以下操作:

To answer your real question, you can do the following:

public static<T> String toStringArrayNonNulls (T[] data) {
    StringBuilder sb = new StringBuilder();
    sb.append("[");
    int n = data.length;
    int i = 0;
    for(; i < n; i++) {
        if(data[i] != null) {
            sb.append(data[i].toString());
            break;
        }
    }
    for(; i < n; i++) {
        if(data[i] != null) {
            sb.append(",");
            sb.append(data[i].toString());
        }
    }
    sb.append("]");
    return sb.toString();
}

然后使用所需的任何类型的数组调用该方法.

And call that method with any type of array you want.

示例

String[] names = new String[] {"Alice",null,"Charly","David",null,null};
System.out.println(toStringArrayNonNulls(names));
Integer[] primes = new Integer[] {2,3,null,null,11};
System.out.println(toStringArrayNonNulls(primes));
Object[] namesAndPrimes = new Integer[] {"Alice",2,null,3,null,"Charly",null,11};
System.out.println(toStringArrayNonNulls(namesAndPrimes));

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