Login | Register   
Twitter
RSS Feed
Download our iPhone app
TODAY'S HEADLINES  |   ARTICLE ARCHIVE  |   FORUMS  |   TIP BANK
Browse DevX
Sign up for e-mail newsletters from DevX


Tip of the Day
Language: Java
Expertise: Beginner
Nov 13, 1998

Use Object.equals(), not ==, for Logical Comparison

One of the most common gotchas for beginning Java programmers involves comparing Objects, especially Strings, with the == operator. Every Object in Java has a unique location in the Java Virtual Machine's memory. The == operator returns true if the two handles on the left and right sides refer to the same location in memory. The function Object.equals() is intended to return true if two handles refer to logically equivalent instances. In the most basic case, this function works by comparing the value of each of the data fields of the two instances and returning true only if they're all equivalent. You should override Object.equals() in your own classes to provide more robust logic:
 
public class StringCompare{
	public static void main(String[] args){
		If(args[0] == "test"){
			System.out.println(args[0] + " == \"test\"");
		}else{
			System.out.println(args[0] + " != \"test\"");
		}

		if(args[0].equals("test")){
			System.out.println(
				args[0] + ".equals(\"test\") == true");
		}else{
			System.out.println(
				args[0] + ".equals(\"test\") == false");
		}
	}
} 
Larry O'Brien
 
Comment and Contribute

 

 

 

 

 


(Maximum characters: 1200). You have 1200 characters left.

 

 

Sitemap