Java如何检查空字符串？
StringUtils.isBlank()方法检查是否该字符串仅包含空格字符，为空或具有null值。如果这些条件为真，则该字符串被视为空白。
还有一个StringUtils.isEmpty()，只有这些方法不检查仅空白字符串。为了检查相反的条件，有StringUtils.isNotBlank()和StringUtils.isNotEmpty()。
使用此方法，我们可以避免重复用于检查空字符串的代码，该代码可能包含更多可键入的代码，然后使用这些便捷方法。
package org.nhooo.example.commons.lang;
import org.apache.commons.lang3.StringUtils;
public class CheckEmptyString {
public static void main(String[] args) {
String var1 = null;
String var2 = "";
String var3 = " \t\t\t";
String var4 = "Hello World";
System.out.println("var1 is blank? = " + StringUtils.isBlank(var1));
System.out.println("var2 is blank? = " + StringUtils.isBlank(var2));
System.out.println("var3 is blank? = " + StringUtils.isBlank(var3));
System.out.println("var4 is blank? = " + StringUtils.isBlank(var4));
System.out.println("var1 is not blank? = " + StringUtils.isNotBlank(var1));
System.out.println("var2 is not blank? = " + StringUtils.isNotBlank(var2));
System.out.println("var3 is not blank? = " + StringUtils.isNotBlank(var3));
System.out.println("var4 is not blank? = " + StringUtils.isNotBlank(var4));
System.out.println("var1 is empty? = " + StringUtils.isEmpty(var1));
System.out.println("var2 is empty? = " + StringUtils.isEmpty(var2));
System.out.println("var3 is empty? = " + StringUtils.isEmpty(var3));
System.out.println("var4 is empty? = " + StringUtils.isEmpty(var4));
System.out.println("var1 is not empty? = " + StringUtils.isNotEmpty(var1));
System.out.println("var2 is not empty? = " + StringUtils.isNotEmpty(var2));
System.out.println("var3 is not empty? = " + StringUtils.isNotEmpty(var3));
System.out.println("var4 is not empty? = " + StringUtils.isNotEmpty(var4));
}
}我们程序的结果是：
var1 is blank? = true var2 is blank? = true var3 is blank? = true var4 is blank? = false var1 is not blank? = false var2 is not blank? = false var3 is not blank? = false var4 is not blank? = true var1 is empty? = true var2 is empty? = true var3 is empty? = false var4 is empty? = false var1 is not empty? = false var2 is not empty? = false var3 is not empty? = true var4 is not empty? = true
Maven依赖
<!-- https://search.maven.org/remotecontent?filepath=org/apache/commons/commons-lang3/3.9/commons-lang3-3.9.jar -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.9</version>
</dependency>