17.7: String Formatting
- Page ID
- 19636
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In Section 3.6, we learned how to use printf
to display formatted output. Sometimes programs need to create strings that are formatted a certain way, but not display them immediately, or ever. For example, the following method returns a time string in 12-hour format:
public static String timeString(int hour, int minute) { String ampm; if (hour < 12) { ampm = "AM"; if (hour == 0) { hour = 12; // midnight } } else { ampm = "PM"; hour = hour - 12; } return String.format("%02d:%02d %s", hour, minute, ampm); }
String.format
takes the same arguments as System.out.printf
: a format specifier followed by a sequence of values. The main difference is that System.out.printf
displays the result on the screen; String.format
creates a new string, but does not display anything.
In this example, the format specifier \%02d
means “two digit integer padded with zeros”, so timeString(19, 5)
returns the string "07:05 PM"
.