Java String isEmpty方法

public boolean isEmpty()

public class Example{  
   public static void main(String args[]){  
    //empty string
    String str1="";  
    //non-empty string
    String str2="hello";  

    //prints true
    System.out.println(str1.isEmpty());  
    //prints false
    System.out.println(str2.isEmpty());  
   }
}

true
false

public class Example{  
   public static void main(String args[]){  
    String str1 = null; 
    String str2 = "beginnersbook";  

    if(str1 == null || str1.isEmpty()){
       System.out.println("String str1 is empty or null"); 
    }
    else{
       System.out.println(str1);
    }
    if(str2 == null || str2.isEmpty()){
       System.out.println("String str2 is empty or null");  
    }
    else{
       System.out.println(str2);
    }
   }
}

String str1 is empty or null
beginnersbook