从java中的字符串数组中删除空值
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Remove Null Value from String array in java
提问by Gnaniyar Zubair
How to remove null value from String array in java?
如何从java中的String数组中删除空值？
String[] firstArray = {"test1","","test2","test4",""};
I need the "firstArray" without null ( empty) values like this
我需要像这样没有空（空）值的“firstArray”
String[] firstArray = {"test1","test2","test4"};
采纳答案by Vivin Paliath
If you want to avoid fencepost errors and avoid moving and deleting items in an array, here is a somewhat verbose solution that uses List:
如果你想避免围栏错误并避免移动和删除数组中的项目，这里有一个有点冗长的解决方案，它使用List：
import java.util.ArrayList;
import java.util.List;
public class RemoveNullValue {
public static void main( String args[] ) {
String[] firstArray = {"test1", "", "test2", "test4", "", null};
List<String> list = new ArrayList<String>();
for(String s : firstArray) {
if(s != null && s.length() > 0) {
list.add(s);
}
}
firstArray = list.toArray(new String[list.size()]);
}
}
Added nullto show the difference between an empty String instance ("") and null.
添加null以显示空 String 实例 ( "") 和null.
Since this answer is around 4.5 years old, I'm adding a Java 8 example:
由于这个答案大约有 4.5 年的历史，因此我添加了一个 Java 8 示例：
import java.util.Arrays;
import java.util.stream.Collectors;
public class RemoveNullValue {
public static void main( String args[] ) {
String[] firstArray = {"test1", "", "test2", "test4", "", null};
firstArray = Arrays.stream(firstArray)
.filter(s -> (s != null && s.length() > 0))
.toArray(String[]::new);
}
}
回答by Mud
Those are zero-length strings, not null. But if you want to remove them:
这些是零长度字符串，而不是 null。但是如果你想删除它们：
firstArray[0] refers to the first element
firstArray[1] refers to the second element
You can move the second into the first thusly:
您可以将第二个移动到第一个中：
firstArray[0] = firstArray[1]
If you were to do this for elements [1,2], then [2,3], etc. you would eventually shift the entire contents of the array to the left, eliminating element 0. Can you see how that would apply?
如果您要对元素 [1,2]、[2,3] 等执行此操作，您最终会将数组的全部内容向左移动，消除元素 0。您能看出这将如何应用吗？
回答by Kirk Woll
If you actually want to add/remove items from an array, may I suggest a Listinstead?
如果您确实想从数组中添加/删除项目，我可以建议List改为吗？
String[] firstArray = {"test1","","test2","test4",""};
ArrayList<String> list = new ArrayList<String>();
for (String s : firstArray)
if (!s.equals(""))
list.add(s);
Then, if you reallyneed to put that back into an array:
然后，如果你真的需要把它放回一个数组中：
firstArray = list.toArray(new String[list.size()]);
回答by Emil
Using Google's guava library
使用谷歌的番石榴库
String[] firstArray = {"test1","","test2","test4","",null};
Iterable<String> st=Iterables.filter(Arrays.asList(firstArray),new Predicate<String>() {
@Override
public boolean apply(String arg0) {
if(arg0==null) //avoid null strings
return false;
if(arg0.length()==0) //avoid empty strings
return false;
return true; // else true
}
});
回答by Ian S.
This is the code that I use to remove null values from an array which does not use array lists.
这是我用来从不使用数组列表的数组中删除空值的代码。
String[] array = {"abc", "def", null, "g", null}; // Your array
String[] refinedArray = new String[array.length]; // A temporary placeholder array
int count = -1;
for(String s : array) {
if(s != null) { // Skips over null values. Add "|| "".equals(s)" if you want to exclude empty strings
refinedArray[++count] = s; // Increments count and sets a value in the refined array
}
}
// Returns an array with the same data but refits it to a new length
array = Arrays.copyOf(refinedArray, count + 1);
回答by akhil_mittal
It seems no one has mentioned about using nonNullmethod which also can be used with streamsin Java 8to remove null (but not empty) as:
似乎没有人提到使用nonNull方法，该方法也可以streams在Java 8 中用于删除 null（但不为空），如下所示：
String[] origArray = {"Apple", "", "Cat", "Dog", "", null};
String[] cleanedArray = Arrays.stream(firstArray).filter(Objects::nonNull).toArray(String[]::new);
System.out.println(Arrays.toString(origArray));
System.out.println(Arrays.toString(cleanedArray));
And the output is:
输出是：
[Apple, , Cat, Dog, , null]
[Apple, , Cat, Dog, ]
[苹果，，猫，狗，，空]
[苹果, , 猫, 狗, ]
If we want to incorporate empty also then we can define a utility method (in class Utils(say)):
如果我们也想合并 empty ，那么我们可以定义一个实用方法（在类中Utils（比如））：
public static boolean isEmpty(String string) {
return (string != null && string.isEmpty());
}
And then use it to filter the items as:
然后使用它来过滤项目：
Arrays.stream(firstArray).filter(Utils::isEmpty).toArray(String[]::new);
I believe Apache common also provides a utility method StringUtils.isNotEmptywhich can also be used.
我相信 Apache common 也提供了一个StringUtils.isNotEmpty也可以使用的实用方法。
回答by 18446744073709551615
A gc-friendly piece of code:
一段 gc 友好的代码：
public static<X> X[] arrayOfNotNull(X[] array) {
for (int p=0, N=array.length; p<N; ++p) {
if (array[p] == null) {
int m=p; for (int i=p+1; i<N; ++i) if (array[i]!=null) ++m;
X[] res = Arrays.copyOf(array, m);
for (int i=p+1; i<N; ++i) if (array[i]!=null) res[p++] = array[i];
return res;
}
}
return array;
}
It returns the original array if it contains no nulls. It does not modify the original array.
如果不包含空值，则返回原始数组。它不会修改原始数组。
