Core Java >> Strings

Best way to check for an empty string

There are multiple ways to find if a string is empty in Java. Even some String utility also provide helper methods to check is the string is empty. By empty string we mean the contents of the string is blank (which is same as “”).

The following program shows how the API methods can be used to check is a string object is empty or not.

package com.example;

/** This class is a Java tutorial for finding empty string
 *
 * @author Extreme Java
 */
public class Test{

	/** This method shows how to check if a string is empty
	 *
	 * @param args
	 */
	public static void main(String[] args) {
		String str="";
		//check empty string by using == operator
		if(str == "") {
			System.out.println("Blank String 1");
		}
		//check empty string by using equals method
		if(str.equals("")) {
			System.out.println("Blank String 1");
		}
		//check empty string by using length method
		if(str.length() ==0 ) {
			System.out.println("Blank String 1");
		}

		String str2 = new String("");
		//check empty string by using == operator
		if(str2 == "") {
			System.out.println("Blank String 2");
		}
		//check empty string by using equals method
		if(str2.equals("")) {
			System.out.println("Blank String 2");
		}
		//check empty string by using length method
		if(str2.length() ==0 ) {
			System.out.println("Blank String 2");
		}
	}
}

output:
Blank String 1
Blank String 1
Blank String 1
Blank String 2
Blank String 2

As the output above shows, the string literal can be checked for emptiness either by using the equals method or the == operator and both the methods return valid results.
But the == operator used with string objects created with new operator will not return valid results for empty check on strings.

The length method can be used safely with any kind of string objects to check if it is empty or not.

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