Back

June 4, 2022

Working With Strings In Java

Overview

1. StringUtils

StringUtils

1. Difference between isNotEmpty() and isNotBlank()
2. When to use StringUtils.equals(s1, s2) and s1.equals(s2)

Difference between isNotEmpty() and isNotBlank()

isNotEmpty()

StringUtils.isNotEmpty(null)    // false
StringUtils.isNotEmpty("")      // false
StringUtils.isNotEmpty(" ")     // true
StringUtils.isNotEmpty("hi")    // true
StringUtils.isNotEmpty(" hi ")  // true

isNotBlank

StringUtils.isNotBlank(null)    // false
StringUtils.isNotBlank("")      // false
StringUtils.isNotBlank(" ")     // false
StringUtils.isNotBlank("hi")    // true
StringUtils.isNotBlank(" hi ")  // true

The only difference between isNotEmpty and isNotBlank is that the former returns true while the latter returns false when the given string contains only whitespaces (e.g. “ “).

Arguably, in most cases, we are usually expecting the string of interest to contain some non-whitespace characters (e.g. “hi”).

As such, prefer to use isNotBlank over isNotEmpty by default unless otherwise specified. Likewise, prefer to use isBlank over isEmpty.

When to use StringUtils.equals(s1, s2) and s1.equals(s2)

StringUtils.equals(s1, s2) provides a null-safe comparison unlike s1.equals(s2).

Consider the scenario below, which option is better?

String s1 = null;
String s2 = "hi";
boolean flag = False;

if (StringUtils.(s1, s2)) {     // null-safe, evaluates to false
    flag = true;
}

if (s1.equals(s2)) {            // throws NullPointerException
    flag = true;
}

It depends on the significance of flag (or whatever code that falls within the if block).

Perhaps you are writing a non-critical application where flag is eventually just a value displayed on the web page. The null-safe option would not cause a break in the program flow (at least within your module/component/application) during runtime and you can always make the fix at a later time.

But what if you are writing a software for a space rocket launch and not updating flag may potentially fail to activate another module at a critical moment? In this case, you might want to use the latter option so that such errorneous scenarios are caught and fixed up front before the software goes live.