将字符串拆分为键值对 [英] Split string into key-value pairs

问题描述

我有这样一个字符串：

  pet：cat :: car：honda :: location：location :: Japan :: food ：sushi 
  

现在：表示键值而 :: 则将这两对分开。
我想将键值对添加到地图中。

我可以使用以下方法来实现这一点：

 地图< String，String> map = new HashMap< String，String>（）; 
 String test =pet：cat :: car：honda :: location：Japan :: food：sushi; 
 String [] test1 = test.split（::）; 
 
 for（String s：test1）{
 String [] t = s.split（：）; 
 map.put（t [0]，t [1]）; 
 
 
（String s：map.keySet（））{
 System.out.println（s +is+ map.get（s））; 
} 
  

但有没有这样做的有效方法？

---

我觉得代码效率低下，因为我已经使用了2 String [] 对象并且调用分割函数两次。
此外，我正在使用 t [0] 和 t [1] ，这可能会抛出<$如果没有值，c $ c> ArrayIndexOutOfBoundsException 你可以做一次调用使用下面的代码对字符串进行split（）和单个传递。但它当然假定String首先是有效的：

  Map< String，String> map = new HashMap< String，String>（）; 
 String test =pet：cat :: car：honda :: location：Japan :: food：sushi; 
 
 //分割'：'和'::'
 String [] parts = test.split（::？）; 
 
 for（int i = 0; i< parts.length; i + = 2）{
 map.put（parts [i]，parts [i + 1]）; 
 
 
（String s：map.keySet（））{
 System.out.println（s +is+ map.get（s））; 
 
  

以上是可能效率稍高一点而不是你的解决方案，但是如果你发现你的代码更加清晰，那么就保留它，因为这样的优化几乎没有机会对性能产生重大影响，除非你做了那么多次。无论如何，如果它是如此重要，那么你应该衡量和比较。

编辑：对于那些想知道的人来说，

在上面的代码中 ::？意味着什么：String.split（）需要一个正则表达式作为参数。分隔符是与正则表达式匹配的子字符串。 ::？是一个正则表达式，意思是：1个冒号，后跟0或1个冒号。因此它允许考虑 :: 和：作为分隔符。

I have a string like this:

pet:cat::car:honda::location:Japan::food:sushi

Now : indicates key-value pairs while :: separates the pairs. I want to add the key-value pairs to a map.

I can achieve this using:

Map<String, String> map = new HashMap<String, String>();
String test = "pet:cat::car:honda::location:Japan::food:sushi";
String[] test1 = test.split("::");

for (String s : test1) {
    String[] t = s.split(":");
    map.put(t[0], t[1]);
}

for (String s : map.keySet()) {
    System.out.println(s + " is " + map.get(s));
}

But is there an efficient way of doing this?

---

I feel the code is inefficient because I have used 2 String[] objects and called the split function twice. Also, I am using t[0] and t[1] which might throw an ArrayIndexOutOfBoundsException if there are no values.

解决方案

You could do a single call to split() and a single pass on the String using the following code. But it of course assumes the String is valid in the first place:

    Map<String, String> map = new HashMap<String, String>();
    String test = "pet:cat::car:honda::location:Japan::food:sushi";

    // split on ':' and on '::'
    String[] parts = test.split("::?");

    for (int i = 0; i < parts.length; i += 2) {
        map.put(parts[i], parts[i + 1]);
    }

    for (String s : map.keySet()) {
        System.out.println(s + " is " + map.get(s));
    }

The above is probably a little bit more efficient than your solution, but if you find your code clearer, then keep it, because there is almost zero chance such an optimization has a significant impact on performance, unless you do that millions of times. Anyway, if it's so important, then you should measure and compare.

EDIT:

for those who wonder what ::? means in the above code: String.split() takes a regular expression as argument. A separator is a substring that matches the regular expression. ::? is a regular expression which means: 1 colon, followed by 0 or 1 colon. It thus allows considering :: and : as separators.

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