本文介绍了如何检查数组是否为空/空?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有一个没有元素的 int
数组,我正在尝试检查它是否为空.
I have an int
array which has no elements and I'm trying to check whether it's empty.
例如,为什么下面代码中 if 语句的条件永远不为真?
For example, why is the condition of the if-statement in the code below never true?
int[] k = new int[3];
if (k == null) {
System.out.println(k.length);
}
推荐答案
null
数组和空数组之间有一个主要区别.这是对 null
的测试.
There's a key difference between a null
array and an empty array. This is a test for null
.
int arr[] = null;
if (arr == null) {
System.out.println("array is null");
}
这里的空"没有官方意义.我选择将空定义为具有 0 个元素:
"Empty" here has no official meaning. I'm choosing to define empty as having 0 elements:
arr = new int[0];
if (arr.length == 0) {
System.out.println("array is empty");
}
空"的另一种定义是如果所有元素都是null
:
An alternative definition of "empty" is if all the elements are null
:
Object arr[] = new Object[10];
boolean empty = true;
for (int i=0; i<arr.length; i++) {
if (arr[i] != null) {
empty = false;
break;
}
}
或
Object arr[] = new Object[10];
boolean empty = true;
for (Object ob : arr) {
if (ob != null) {
empty = false;
break;
}
}
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