Comparing strings in an if: !string.equals("") vs !"".equals(string)

Question

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Difference between these two conditions?

I am doing some code cleanup and NetBeans made a suggestion to change

if(!billAddress1.equals("")) to if (!"".equals(billAddress1)).

What is the difference between the two, and the advantages of using the suggested version over the readability of the original version?

See this post: - http://stackoverflow.com/questions/13084049/difference-between-these-two-conditions/13084072#13084072 — Rohit Jain, Nov 20 '12 at 19:27
Add this question: http://stackoverflow.com/questions/9888508/string-equals-argument-ordering — hmjd, Nov 20 '12 at 19:28
Well it seems I have a resounding answer to this question :) Thanks everyone, answer will be accepted once min time is up. — Robert H, Nov 20 '12 at 19:29

score 8 · Accepted Answer · answered Nov 20 '12 at 19:27

8

billAddress1.equals("") will cause a NullPointerException if billAddress1 is null, "".equals(billAddress1) wont.

answered Nov 20 '12 at 19:27

jlordo

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score 3 · Answer 2 · answered Nov 20 '12 at 19:27

3

// Could cause a NullPointerException if billAddress1 is null
if(!billAddress1.equals(""))

// Will not cause a NullPointerException if billAddress1 is null
if (!"".equals(billAddress1))

answered Nov 20 '12 at 19:27

Ruan Mendes

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score 3 · Answer 3 · answered Nov 20 '12 at 19:27

3

!"".equals(billAddress1) will never cause an NPE, so it allows a more compact syntax by allowing to get rid of the billAddress1 == null that would otherwise be required.

answered Nov 20 '12 at 19:27

Samuel Rossille

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score 2 · Answer 4 · answered Nov 20 '12 at 19:28

2

The latter will not cause a Null pointer exception if the value is null.

answered Nov 20 '12 at 19:28

DaBaer

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score 2 · Answer 5 · answered Nov 20 '12 at 19:32

2

One saves you from NPE as others have pointed out. But if you are sure it's not going to be null then the better way to check if a string is empty is to use the String.isEmpty() method, that's what the code seems to be trying to do.

answered Nov 20 '12 at 19:32

Bhesh Gurung

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score 1 · Answer 6 · answered Nov 20 '12 at 19:29

1

The first one has a potential to cause NullPointerException.

answered Nov 20 '12 at 19:29

droidchef

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Comparing strings in an if: !string.equals("") vs !"".equals(string)

6 Answers6