![]() ![]() ![]() When our string was padded, it was right-justified (leading String is truncated after the first five characters. Limit the length of the string displayed, so our “Happy Birthday” In the secondĮxample, we used the literal. Resulting in spaces being added to pad our argument. In the first case, we specified a width of five characters, printf ( "String is '%.5s'\n", "Happy Birthday!" ) // String is 'Happy' printf ( "String is '%5s'\n", "A" ) // String is ' A' System. Precision changes meaning slightly and controls the number of digitsĭisplayed after the decimal point. As we’ll see later, for floating-point numeric types, the The width and precision fieldsĬontrol the size of the output for text and the number of digitsįor simple text arguments, you can think of the widthĪnd precision as a minimum and maximum number of characters to be Or more special flag characters governing the format. Individual arguments in the variable-length argument list by referring The argument index can be used to reorder or reuse We’llĭiscuss these as they come up, but here’s the rundown. Number of optional items before the conversion type character. The general layout of the embedded format string is asįollows: % conversion_type ForĮxample, with floating-point numbers, you can specify a precision in the Layout with different meanings for different types of arguments. Third, additional flags and fields can be used to govern Type-specific conversion characters, printf can take into account language-specific By telling the Formatter the type of argument with Second, theĬapable of displaying numbers, percentages, dates, and times in manyĭifferent languages just by specifying a Locale as an argument. Garbage in our string (and your IDE may flag it as well). Get a runtime IllegalFormatConversionException instead of If we make a mistake in the arguments, we By specifying %d, we ensure that only an integer type isįormatted at that location. Specialized conversion characters accomplish three things. Of displaying the numeric age argument just as well as %d. For example, the %s general stringĬonversion in our previous example would actually have handled the job We cover the basics here and return to dateĪt first glance, some of the conversion characters may not seem toĭo much. There are about a dozen basicĬonversion characters corresponding to different types and primitivesĪnd there are a couple of dozen more that are specifically used forįormatting dates and times. The first conversion character is s, the most general format, which represents a Strings: "My name is %s and I am %d years old." For example, the following text has two embedded format The simplestįormat string is just a percent sign (%) followed by a conversionĬharacter. The syntax of the format string is compact and a bitĬryptic at first, but not bad once you get used to it. It’s there solely as a shout-out to the C programmers and ex-C ![]() The printf() method is identical to and, in fact, Method, PrintStream and PrintWriter also have a version of the format In Chapter 12, but this simply means that youįormatting for writing strings to any kind of stream, whether it be to format ( "My name is %s and I am %d years old.", name, age ) Ĭlasses, which are used for writing text to streams, have their own With arguments (like the C language sprintf() method): String message = String. Several convenience methods can hide the Formatter object from you and you may not need The primary new tool in our text formatting arsenal is the (We mention this to explain why these similar APIs both Variable-length argument lists and autoboxing of primitive types wereĪdded in Java 5.0. Although Java has had some text formattingĬapabilities in the past (we’ll discuss the java.text package and MessageFormat later), printf formatting was not really feasible until Java has extended the concept, adding some additional type safety andĬonvenience features. printf ( "My name is %s and I am %d years old\n", name, age ) įunction, so if you’ve done any C programming, this will look familiar. Here is a quick example of printf-formatted output: System. Methods also make use of variable-length argument lists, which makes Strings embedded into text to tell the formatting engine where to placeĪrguments and give detailed specification about conversions, layout, and printf-style formatting utilizes special format A standard feature that Java adopted from the C language is printf-style string formatting.
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