Java Formatting, Dates, and Localization Flashcards

Which class should be used to format a number as currency for a specific locale in Java?

Answer: java.text.NumberFormat obtained via NumberFormat.getCurrencyInstance(locale)

`NumberFormat.getCurrencyInstance(Locale)` returns a NumberFormat preconfigured for the currency of the given locale. While DecimalFormat can approximate it, the standard SCJP answer is `NumberFormat.getCurrencyInstance()`. java.util.Currency represents a currency but doesn't format numbers.

What is the output of `System.out.printf("%05.1f%n", 3.5);`?

Answer: 003.5

The format `%05.1f` means: width 5, zero-padded, 1 decimal place. '3.5' formatted to 1 decimal is '3.5' (3 chars). To reach width 5, two zeros are prepended: '003.5'. The `%n` emits a platform-specific newline.

Which statement about `java.util.Calendar` is TRUE in Java SE 6?

Answer: Calendar.MONTH is zero-based (January = 0)

Calendar.MONTH is notoriously zero-based: January = 0, February = 1, … December = 11. DAY_OF_MONTH is 1-based. Calendar is mutable, and you cannot instantiate it directly — you use Calendar.getInstance() because the constructor is protected.

Which of the following correctly creates a Locale for French as spoken in France?

Answer: new Locale("fr", "FR")

The Locale(String language, String country) constructor takes ISO 639-1 language code ('fr') and ISO 3166-1 country code ('FR'). Language codes are lowercase, country codes are uppercase. 'France' and 'French' are display names, not codes.

What does `DateFormat.getDateInstance(DateFormat.SHORT, locale)` return?

Answer: A DateFormat that formats only dates in a short locale-specific style

`DateFormat.getDateInstance(style, locale)` returns a date-only formatter (no time portion) styled appropriately for the locale. SHORT typically yields something like '7/30/26' in the US, but the actual format depends on the locale — it is locale-sensitive, not hard-coded.

What is the output of the following code? String s = String.format("%-10s|", "hi");

Answer: "hi |"

The `%-10s` format specifier means: string, width 10, left-aligned (the `-` flag). 'hi' is 2 characters, so 8 spaces are appended to reach width 10, followed by '|'. Result: 'hi |'.