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printf string formatting

O. Ziggy
Ranch Hand

Joined: Oct 02, 2005
Posts: 430

In the following program

The output is

Can someone please explain how a double value (i.e. 123.456) is converted to a boolean (ie. true)

Henry Wong

Joined: Sep 28, 2004
Posts: 18991

It's all explained, in the JavaDoc of the java.util.Formatter class, which is the class that is used to format the text.


Books: Java Threads, 3rd Edition, Jini in a Nutshell, and Java Gems (contributor)
O. Ziggy
Ranch Hand

Joined: Oct 02, 2005
Posts: 430

Yes i saw the description in the API.

If the argument arg is null, then the result is "false". If arg is a boolean or Boolean, then the result is the string returned by String.valueOf(arg). Otherwise, the result is "true".

It just seemed weird that any string can result in a value of true. For example, the following expression also prints true.

Paul Clapham

Joined: Oct 14, 2005
Posts: 18907

You're better off believing what the documentation says, rather than what your intuition says. For one thing that's how the JVM is actually going to work.
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subject: printf string formatting