Java Data Type - 如何检查字符串是否为空

To test whether a String object is empty. 
The length of an empty string is zero. 



There are three ways to check for an empty string:


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



The following code shows how to use the three methods:


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
    boolean empty2 = str2.isEmpty(); // Assigns true to empty1

    // Using the equals() method
    boolean empty3 = "".equals(str1); // Assigns false to empty3
    boolean empty4 = "".equals(str2); // Assigns true to empty4

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

  }
}