Best approach would be to use Apache Commons StringUtils.isBlank(String)
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.9</version>
</dependency>
- uses a commonly used library
- proven
- uses centralized code
- is very similar to the source that has to be converted
- Not falling for 'Not invented here' syndrome
Useful method from Apache Commons:
org.apache.commons.lang.StringUtils.isBlank(String str)
https://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/StringUtils.html#isBlank(java.lang.String)
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)){...}
StringUtils.isBlank() checks that each character of the string is a whitespace character (or that the string is empty or that it's null). This is totally different than just checking if the string is empty.
From the linked documentation:
Checks if a String is whitespace, empty ("") or null.
StringUtils.isBlank(null) = true StringUtils.isBlank("") = true StringUtils.isBlank(" ") = true StringUtils.isBlank("bob") = false StringUtils.isBlank(" bob ") = false
For comparison StringUtils.isEmpty:
StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false
Warning: In java.lang.String.isBlank() and java.lang.String.isEmpty() work the same except they don't return true for null.
java.lang.String.isBlank() (since Java 11)
java.lang.String.isEmpty()
The accepted answer from @arshajii is totally correct. However just being more explicit by saying below,
StringUtils.isBlank()
StringUtils.isBlank(null) = true
StringUtils.isBlank("") = true
StringUtils.isBlank(" ") = true
StringUtils.isBlank("bob") = false
StringUtils.isBlank(" bob ") = false
StringUtils.isEmpty
StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false
In the class org.apache.commons.lang3.StringUtils, the function isBlank is like this:
public static boolean isBlank(final CharSequence cs) {
int strLen;
if (cs == null || (strLen = cs.length()) == 0) {
return true;
}
for (int i = 0; i < strLen; i++) {
if (!Character.isWhitespace(cs.charAt(i))) {
return false;
}
}
return true;
}
It works well for Java 8, you just have to import it
Before Java 11: string.trim().isEmpty();
so, if you want wrap isBlank function, you can do as follow:
public static final boolean isBlank(final String text) {
return text == null || text.trim().isEmpty();
}
I have some config file and it is deployed in many regions. Some regions have certain requirements for example lets say one region needed a username and password (basic auth). The current setup is that each deployment has it's own config file and only the instances where it is needed are these values included in the respective config.xml file.
So I have in my Java code some logic that says
'if this element is in the XML, set the corresponding variable with its value, if not do nothing'
So when I'm trying to see if that value is present or if the tag is empty/blank, which String utility should I use to check?
example code (default option left open as empty string):
if (my_config.getString(USER_ID_ELEMENT, "") != null
& my_config.getString(PASSWORD_ELEMENT, "") != null) {
my_userId = m_config.getString(USER_ID_ELEMENT, "");
my_password = m_config.getString(PASSWORD_ELEMENT, "");Here I'm checking if it is not null, but I don't think it's a very good test since I don't know if an empty XML tag is blank or is empty (i think null isn't even an option)?