java 使用空值对数组进行排序
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Sorting array with null values
提问by jl90
I have a program that allows user to delete an element from an array and I am trying to sort them in alphabetic order using compareTo(); through a for loop. However, the null values are giving me problems. For example an array with null values:
我有一个程序允许用户从数组中删除一个元素，我正在尝试使用 compareTo() 按字母顺序对它们进行排序；通过 for 循环。但是，空值给我带来了问题。例如具有空值的数组：
String[] myArray = {"Apple", "Banana", null, "Durian", null, null, "Grapes"};
When Java is comparing them and reads a null value, it would give me a NullPointerException.
当 Java 比较它们并读取空值时，它会给我一个 NullPointerException。
Is there any way that I can sort this array with null values at the back? For example:
有什么办法可以在后面用空值对这个数组进行排序吗？例如：
{"Apple", "Banana", "Durian", "Grapes", null, null, null}
I know that using Vectors can solve the problem but I am just curious if there is any way that I can just do it without changing my array to vectors.
我知道使用 Vectors 可以解决问题，但我很好奇是否有任何方法可以在不将数组更改为向量的情况下做到这一点。
回答by Evgeniy Dorofeev
try this
试试这个
Arrays.sort(myArray, new Comparator<String>() {
@Override
public int compare(String o1, String o2) {
if (o1 == null && o2 == null) {
return 0;
}
if (o1 == null) {
return 1;
}
if (o2 == null) {
return -1;
}
return o1.compareTo(o2);
}});
it produces the required order
它产生所需的订单
回答by AlexWien
write your own Comparatorthat accepts null values, and pass that comparator to the Arrays.sort() method
编写自己的Comparator接受空值的方法，并将该比较器传递给Arrays.sort() 方法
