Converting a string into a boolean condition

Question

Say I have a String

String strCondition = something.contains("value") && somethingElse.equals("one");

How do I convert this String into a boolean condition so that I can be able to use it in an IF statement?

If I use valueOf(), will it evaluate the contents of the String?

RE-EDIT: I am not sure how to put this.

I am taking the value something.contains("value") && somethingElse.equals("one") from a database column. If I try to assign that to boolean variable it shows a type mismatch.

If you have multiple strings but a fixed set of them, then you can go for creating an enum out of them and then comparing them — AurA, Jun 18 '14 at 06:27
How do you even store the boolean value into a String in the first place? — Rahul, Jun 18 '14 at 06:27
This won't even compile. Firstly, `&&` returns type `boolean`. Secondly, `String.contains()` is misspelled. — Unihedron, Jun 18 '14 at 06:28
I think this could possibly be just a really badly communicated version of "how do I turn a string into code that I can use in a program later?" — awksp, Jun 18 '14 at 06:29
"If I use valueOf(), will it evaluate the contents of the String?" Have you checked the Oracle docs? They might mention it. — Unihedron, Jun 18 '14 at 06:33
OP: You might want to check [this](https://stackoverflow.com/questions/4389232/run-piece-of-code-contained-in-a-string) out. Reflection may or may not be an option, depending on if the structure of `strCondition` is predictable. — awksp, Jun 18 '14 at 06:37
I don't think that even compiles `String strCondition = something.contains("value") && somethingElse.equals("one");`. As mentioned by others the expression is already a `boolean` — Eypros, Jun 18 '14 at 07:04

Stultuske · Accepted Answer · 2018-03-30T05:59:33.210

you don't.

it already is a boolean expression.

something.contains("value") -> this returns either true or false && somethingElse.equals("one"); -> this also returns true or false.

what you need, is either:

boolean strCondition = something.contains("value") && somethingElse.equals("one");
if ( strCondition )

or

if ( something.contains("value") && somethingElse.equals("one"))

EDIT:

The above would either return true, false, or throw a nasty NullPointerException.

To avoid the latter, you should use:

if ( "one".equals(somethingElse) && (something != null && something.contains("value"))

score 3 · Answer 2 · answered Jun 18 '14 at 06:31

3

You can use these :

if (strCondition.equals("true")) 

if (Boolean.getBoolean(strCondition)) 

if (Boolean.valueOf(strCondition))

answered Jun 18 '14 at 06:31

PurkkaKoodari

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score 2 · Answer 3 · answered Jun 18 '14 at 06:27

2

something.contains("value") && somethingElse.equals("one");// returns a boolean . why put it into a String in the first place?

answered Jun 18 '14 at 06:27

TheLostMind

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MariuszS · Answer 4 · 2014-06-18T06:32:49.770

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Read JavaDoc first!

Boolean.valueOf(String s) returns a Boolean with a value represented by the specified string. The Boolean returned represents a true value if the string argument is not null and is equal, ignoring case, to the string "true".

Sample code

if(Boolean.valueOf(strCondition)) {

}

edited Jun 18 '14 at 06:32

answered Jun 18 '14 at 06:27

MariuszS

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score 1 · Answer 5 · answered Jun 18 '14 at 06:30

1

contains and equals methods of string returns boolean you cannot cast to String

answered Jun 18 '14 at 06:30

A Stranger

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Converting a string into a boolean condition

5 Answers5