Java String isEmpty()

The Java String class isEmpty() method checks if the input string is empty or not. Note that here empty means the number of characters contained in a string is zero.

Signature

The signature or syntax of string isEmpty() method is given below:

Returns

true if length is 0 otherwise false.

Since

1.6

Internal implementation

Java String isEmpty() method example

FileName: StringIsEmptyExample.java

  public class IsEmptyExample{  public static void main(String args[]){  String s1=””;  String s2=”tutoraspire”;    System.out.println(s1.isEmpty());  System.out.println(s2.isEmpty());  }}  

Test it Now

Output:

true  false

Java String isEmpty() Method Example 2

FileName: StringIsEmptyExample2.java

  public class IsEmptyExample2 {  public static void main(String[] args) {  String s1=””;    String s2=”Tutoraspire”;      // Either length is zero or isEmpty is true  if(s1.length()==0 || s1.isEmpty())  System.out.println(“String s1 is empty”);  else System.out.println(“s1”);  if(s2.length()==0 || s2.isEmpty())  System.out.println(“String s2 is empty”);  else System.out.println(s2);  }  }  

Output:

String s1 is empty TutorAspire

Empty Vs. Null Strings

Earlier in this tutorial, we have discussed that the empty strings contain zero characters. However, the same is true for a null string too. A null string is a string that has no value.

  String str = “”; // empty string  String str1 = null; // null string. It is also not containing any characters.  

The isEmpty() method is not fit for checking the null strings. The following example shows the same.

FileName: StringIsEmptyExample3.java

  public class StringIsEmptyExample3   {  // main method  public static void main(String argvs[])  {  String str = null;  if(str.isEmpty())  {  System.out.println(“The string is null.”);  }  else  {  System.out.println(“The string is not null.”);  }  }  }  

Output:

Exception in thread "main" java.lang.NullPointerException  at StringIsEmptyExample3.main(StringIsEmptyExample3.java:7)

Here, we can use the == operator to check for the null strings.

FileName: StringIsEmptyExample4.java

  class StringIsEmptyExample4  {  // main method  public static void main(String argvs[])  {  String str = null;  if(str == null)  {  System.out.println(“The string is null.”);  }  else  {  System.out.println(“The string is not null.”);  }  }  }  

Output:

The string is null.

Blank Strings

Blank strings are those strings that contain only white spaces. The isEmpty() method comes in very handy to check for the blank strings. Consider the following example.

FileName: StringIsEmptyExample5.java

  public class StringIsEmptyExample5   {  // main method  public static void main(String argvs[])  {  // a blank string  String str = ”     “;  int size = str.length();    // trim the white spaces and after that  // if the string results in the empty string   // then the string is blank; otherwise, not.  if(size == 0)  {  System.out.println(“The string is empty. n”);  }  else if(size > 0 && str.trim().isEmpty())  {  System.out.println(“The string is blank. n”);  }  else  {  System.out.println(“The string is not blank. n”);  }    str = ” Welcome to TutorAspire .  “;  size = str.length();  if(size == 0)  {  System.out.println(“The string is empty. n”);  }  if(size > 0 && str.trim().isEmpty())  {  System.out.println(“The string is blank. n”);  }  else  {  System.out.println(“The string is not blank. n”);  }  }  }  

Output:

The string is blank.   The string is not blank.

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Java String isEmpty()

Signature

Returns

Since

Internal implementation

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Blank Strings

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