Java - String Empty Value Check

Introduction

The length of an empty string is zero.

To test whether a String object is empty. There are three ways to check for an empty string:

• Use the isEmpty() method.
• Use the equals() method.
• Get the length of the String and check if it is zero.

The following snippet of code shows how to use the three methods:

The second method is preferred as it handles the comparison with null gracefully.

The first and third methods throw a NullPointerException if the string is null.

The second method returns false when the string is null, for example, "".equals(null) returns false.

Demo

public class Main {
  public static void main(String[] args) {
    String str1 = "Hello";
    String str2 = "";

    // Using the isEmpty() method
    boolean empty1 = str1.isEmpty(); // Assigns false to empty1
    System.out.println(empty1);/*from  w  w  w  .j a v  a 2 s  .c  o m*/
    boolean empty2 = str2.isEmpty(); // Assigns true to empty1
    System.out.println(empty2);
    
    // Using the equals() method
    boolean empty3 = "".equals(str1); // Assigns false to empty3
    System.out.println(empty3);
    boolean empty4 = "".equals(str2); // Assigns true to empty4
    System.out.println(empty4);

    // Comparing length of the string with 0
    boolean empty5 = str1.length() == 0; // Assigns false to empty5
    System.out.println(empty5);
    boolean empty6 = str2.length() == 0; // Assigns true to empty6
    System.out.println(empty6);

  }
}

Result

Exercise

• Write code to return default value If string is Blank
• Write code to return default If string Empty
• Write code to return default value If string is Null
• Write code to add an empty item in the string array.
• Write code to check if all elements in an array is Empty String
• Write code to check if String array has Any Empty element
• Write code to check if a string is Not Empty
• Write code to return default String if the string parameter is empty
• Write code to create function to check if a string is Empty or null
• Write code to create a function to check if a string is Empty
• Write code to create a function to check if a string is not Empty
• Write code to create a function to check if a string is Null Or Empty
• Write code to Check whether all string values in given array is null or empty.
• Write code to Checks if a String is whitespace, empty ("") or null. Using two return statements
• Write code to check if a string is Empty using multiple or || statements
• Write code to check if a string is Null Or Empty by comparing with empty space
• Write code to Check whether a collection is empty or null.
• Write code to Returns an empty String if string is null.

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