How to use the trim() function of the String class in Java to remove the leading and trailing spaces of a string and remove the excess spaces in the middle at the same time

How does Java use the trim() function of the String class to remove the leading and trailing spaces of a string, and at the same time remove the extra spaces in the middle?

In Java, the String class is a frequently used class, and it provides many Convenience method to manipulate strings. One of the commonly used methods is the trim() function, which can remove leading and trailing spaces from a string. But by default, the trim() function can only remove leading and trailing spaces, but cannot remove excess spaces in the middle. This article will introduce how to use the trim() function to remove leading and trailing spaces from a string, as well as remove excess spaces in the middle.

First of all, you need to understand the function of trim() function. The trim() function is an instance method of the String class, which can remove leading and trailing spaces from a string. The return value of the trim() function is a new string, and the original string has not been changed. The following is a simple example:

String str = "   Hello world!   ";
String trimmedStr = str.trim();
System.out.println(trimmedStr);

Running the above code will output "Hello world!", and you can see that the leading and trailing spaces have been removed.

Next, we need to solve the problem of how to remove the extra spaces in the middle. A simple way is to use regular expressions to match and replace extra spaces. Here is an example:

String str = "   Hello    world!   ";
String trimmedStr = str.trim().replaceAll("\s+", " ");
System.out.println(trimmedStr);

Running the above code will output "Hello world!", and you can see that the extra spaces in the middle have been removed.

The above code uses the trim() function to remove leading and trailing spaces from the string, and then uses the replaceAll() function to match and replace excess spaces. Where "\s" is a regular expression representing one or more spaces. " " is the replaced content, which is a space.

Another method is to use the split() function to split the string and then rejoin it into a string with excess spaces removed. The following is an example:

String str = "   Hello    world!   ";
String[] words = str.trim().split("\s+");
String trimmedStr = String.join(" ", words);
System.out.println(trimmedStr);

Running the above code will output "Hello world!", the effect is the same as the previous example.

The above is a method of using the trim() function of the String class to remove the leading and trailing spaces of the string and remove the excess spaces in the middle. Through the above example, we can see that the combination of the trim() function and regular expressions is a simple and effective method that can quickly remove spaces from strings. In actual development, if you need to remove leading and trailing spaces from a string and remove excess spaces in the middle, you can use the above method.

To summarize, the trim() function of the String class in Java can remove the leading and trailing spaces of the string, but it cannot remove the extra spaces in the middle. To remove leading and trailing spaces as well as excess spaces in the middle of a string at the same time, you can use regular expressions or the split() function to match and replace excess spaces. I hope this article will help you understand and use the trim() function.

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