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javastring-formatting

What does this 'String.format("...");' in Java do?

String.format("%-" + 3 + "." + 3 + "s", givenString);

This is supposed to add white spaces but it doesn't. I tried it on an online compiler and it adds up the numbers to the string. I don't understand what that's doing. Could someone explain?

Solution

  • public static String format(String format, Object... args) - this is the method declaration.

    String format = "%-" + 3 + '.' + 3 + 's';   // = %-3.3s
String.format(format, givenString);

    This is used to build format dynamically, but it does not have variables in it, so you could replace it with String.format("%-3.3s", givenString);

    According to format, this prints a string with a maximum of 3 characters in length. It reserves 3 symbols per line and it will be left justified in case givenString is less than 3 characters long.

    Demo:

    System.out.println(String.format("%-3.3s", "ab"));  // "ab "
System.out.println(String.format("%-3.3s", "abc"));  // "abc"
System.out.println(String.format("%-3.3s", "abcd"));  // "abc"
System.out.println(String.format("%-3.3s", "a") + String.format("%-3.3s", "b"));  // "a  b  "

    See more in Documentation