i am sure this must have been asked before in different ways - as isEmptyOrNull is so common yet people implement it differently. but i have below curious query in terms of best available approach which is good for memory and performance both.
1) Below does not account for all spaces like in case of empty XML tag
return inputString==null || inputString.length()==0;
2) Below one takes care but trim can eat some performance + memory
return inputString==null || inputString.trim().length()==0;
3) Combining one and two can save some performance + memory (As Chris suggested in comments)
return inputString==null || inputString.trim().length()==0 || inputString.trim().length()==0;
4) Converted to pattern matcher (invoked only when string is non zero length)
private static final Pattern p = Pattern.compile("\\s+");
return inputString==null || inputString.length()==0 || p.matcher(inputString).matches();
5) Using libraries like -
Apache Commons (StringUtils.isBlank/isEmpty
)
or Spring (StringUtils.isEmpty
)
or Guava (Strings.isNullOrEmpty
)
or any other option?
To detect if a string is null or empty, you can use the following without including any external dependencies on your project and still keeping your code simple/clean:
if(myString==null || myString.isEmpty()){
//do something
}
or if blank spaces need to be detected as well:
if(myString==null || myString.trim().isEmpty()){
//do something
}
you could easily wrap these into utility methods to be more concise since these are very common checks to make:
public final class StringUtils{
private StringUtils() { }
public static bool isNullOrEmpty(string s){
if(s==null || s.isEmpty()){
return true;
}
return false;
}
public static bool isNullOrWhiteSpace(string s){
if(s==null || s.trim().isEmpty()){
return true;
}
return false;
}
}
and then call these methods via:
if(StringUtils.isNullOrEmpty(myString)){...}
and
if(StringUtils.isNullOrWhiteSpace(myString)){...}
Just to show java 8's stance to remove null values.
String s = Optional.ofNullable(myString).orElse("");
if (s.trim().isEmpty()) {
...
}
Makes sense if you can use Optional<String>
.
If you have to test more than one string in the same validation, you can do something like this:
import java.util.Optional;
import java.util.function.Predicate;
import java.util.stream.Stream;
public class StringHelper {
public static Boolean hasBlank(String ... strings) {
Predicate<String> isBlank = s -> s == null || s.trim().isEmpty();
return Optional
.ofNullable(strings)
.map(Stream::of)
.map(stream -> stream.anyMatch(isBlank))
.orElse(false);
}
}
So, you can use this like StringHelper.hasBlank("Hello", null, "", " ")
or StringHelper.hasBlank("Hello")
in a generic form.
With the openJDK 11 you can use the internal validation to check if the String is null or just white spaces
import jdk.internal.joptsimple.internal.Strings;
...
String targetString;
if (Strings.isNullOrEmpty(tragetString)) {}
This one from Google Guava could check out "null and empty String" in the same time.
Strings.isNullOrEmpty("Your string.");
Add a dependency with Maven
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>20.0</version>
</dependency>
with Gradle
dependencies {
compile 'com.google.guava:guava:20.0'
}
Optional.ofNullable(label)
.map(String::trim)
.map(string -> !label.isEmpty)
.orElse(false)
OR
TextUtils.isNotBlank(label);
the last solution will check if not null and trimm the str at the same time
springframework library Check whether the given String is empty.
f(StringUtils.isEmpty(str)) {
//.... String is blank or null
}
You can make use of Optional and Apache commons Stringutils library
Optional.ofNullable(StringUtils.noEmpty(string1)).orElse(string2);
here it will check if the string1 is not null and not empty else it will return string2
Apache Commons Lang has StringUtils.isEmpty(String str)
method which returns true if argument is empty or null
if (str == null || str.trim().length() == 0) {
// str is empty
}
In most of the cases, StringUtils.isBlank(str)
from apache commons library would solve it. But if there is case, where input string being checked has null value within quotes, it fails to check such cases.
Take an example where I have an input object which was converted into string using String.valueOf(obj)
API. In case obj reference is null, String.valueOf returns "null" instead of null.
When you attempt to use, StringUtils.isBlank("null")
, API fails miserably, you may have to check for such use cases as well to make sure your validation is proper.
Useful method from Apache Commons:
org.apache.commons.lang.StringUtils.isBlank(String str)
Source: Stackoverflow.com