Java: String to Boolean

Question

I have to read a String from a field and then convert it to a Boolean.
I've tried this:

ObjectInputStream nm;
nm = new ObjectInputStream(new FileInputStream("buscamines.txt"));
String s = nm.readLine();
Boolean bool = Boolean.valueOf(s);

But it's not working, when I print the string s, it is correct but the Boolean value is always false.

Is there any other way to convert a String to Boolean?

You wrote in your question: when I print the String s, it is correct Perhaps s contains leading (or trailing) spaces? Perhaps it contains non-printing characters? I presume that the value of s is true. I suggest you print the length of s and see whether it is 4. — Abra
– Abra, Commented Jun 6, 2020 at 18:01

Alessio Cantarella · Accepted Answer · 2020-06-06 18:10:04Z

3

According to Java's Boolean documentation:

public static 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".

So, it means that:

System.out.print(Boolean.valueOf("true")); // -> true
System.out.print(Boolean.valueOf("TRUE")); // -> true
System.out.print(Boolean.valueOf("tRuE")); // -> true
System.out.print(Boolean.valueOf("false")); // -> false
System.out.print(Boolean.valueOf("anything else")); // -> false
System.out.print(Boolean.valueOf("TRUE ")); // -> false

edited Jun 6, 2020 at 18:10

answered Jun 6, 2020 at 17:54

Alessio Cantarella

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2 Comments

Abra Over a year ago

What Boolean value is obtained for the string "TRUE " (i.e. with a trailing space) ?

Alessio Cantarella Over a year ago

@Abra System.out.print(Boolean.valueOf("TRUE ")); will return false.

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