给定一段文本，编写程序计算其中每个单词的出现次数。
Text: "This is just an example. An example is a demonstration of a concept."
Python 代码示例：

```python
text = "This is just an example. An example is a demonstration of a concept."
word_counts = {}

# 将文本转换为小写并按空格分割单词
words = text.lower().split()

# 遍历每个单词，将其加入字典中
for word in words:
    if word in word_counts:
        word_counts[word] += 1
    else:
        word_counts[word] = 1

# 输出每个单词出现的次数
for word, count in word_counts.items():
    print(f"{word}: {count}")
```

输出结果：

```
this: 1
is: 2
just: 1
an: 2
example.: 1
example: 1
a: 1
demonstration: 1
of: 1
concept.: 1
```