Java，如果列表中的修剪字符串包含字符串，则返回

Question

In Java, I want to check whether a String exists in a List<String> myList .

Something like this:

if(myList.contains("A")){
    //true
}else{
    // false
}

The problem is myList can contain un-trimmed data:

{'  A', 'B  ', '  C  '}

I want it to return true if my item 'B' is in the list. How should I do this? I would like to avoid a looping structure.

Answer 1

With Java 8 Stream API:

List<String> myList = Arrays.asList("  A", "B  ", "  C  ");
return myList.stream().anyMatch(str -> str.trim().equals("B"));

Answer 2

You need to iterate your list and call String#trim for searching:

String search = "A";
for(String str: myList) {
    if(str.trim().contains(search))
       return true;
}
return false;

OR if you want to perform ignore case search , then use:

search = search.toLowerCase(); // outside loop

// inside the loop
if(str.trim().toLowerCase().contains(search))

Answer 3

You can do it in a single line by using regex:

if (myList.toString().matches(".*\\bA\\b.*"))

This code should perform quite well.

---

BTW, you could build the regex from a variable, like this:

.matches("\\[.*\\b" + word + "\\b.*]")

I added [ and ] to each end to prevent a false positive match when the search term contains an open/close square bracket at the start/end.

Answer 4

String search = "A";
for(String s : myList)
    if(s.contains(search)) return true;
return false;

This will iterate over each string in the list, and check if it contains the string you're looking for. If it's only spaces you want to trap for, you can do this:

String search = "A";
for(String s : myList)
    if(s.replaceAll(" ","").contains(search)) return true;
return false;

which will first replace spaces with empty strings before searching. Additionally, if you just want to trim the string first, you can do:

String search = "A";
for(String s : myList)
    if(s.trim().contains(search)) return true;
return false;

Answer 5

Try this:

for(String str: myList) {
    if(str.trim().equals("A"))
       return true;
}
return false;

You need to use str.equals or str.equalsIgnoreCase instead of contains because contains in string works not the same as contains in List

List<String> s = Arrays.asList("BAB", "SAB", "DAS");
s.contains("A"); // false
"BAB".contains("A"); // true

Answer 6

You can use your own code. You don't need to use the looping structure, if you don't want to use the looping structure as you said above. Only you have to focus to remove space or trim the String of the list.

If you are using java8 you can simply trim the String using the single line of the code:

myList = myList.stream().map(String :: trim).collect(Collectors.toList());

The importance of the above line is, in the future, you can use a List or set as well. Now you can use your own code:

if(myList.contains("A")){
    //true
}else{
    // false
}

Answer 7

您可以使用近似字符串匹配库来执行此操作，例如SecondString ，但这几乎肯定是矫枉过正——只需使用提供的 for-loop 答案之一即可。