String Formatting

Upper and Lowercase

We can change the case of strings with .toUpperCase() and .toLowerCase().

java

String quote = "The house on Mango Street isn’t it.";

System.out.println(quote.toUpperCase());
System.out.println(quote.toLowerCase());

output

THE HOUSE ON MANGO STREET ISN’T IT.
the house on mango street isn’t it.

Slice

We can extract a portion of a string using the substring() method.

java

String quote = "The house on Mango Street isn’t it.";
System.out.println(quote.substring(13, 25));

output

Mango Street

String Formatting

We can interpolate values into strings using String.format.

java

String author = "Min Jin Lee";
String book = "Pachinko";
int year = 2017;

String summary = String.format("%s wrote %s in %d", author, book, year);
System.out.println(summary);

output

Min Jin Lee wrote Pachinko in 2017

Formatting Numbers

We can use String.format to format numbers with a specific number of decimal places.

TIP

Note that trailing 0s are included, which makes it good for formatting currency.

java

double price = 2.39782;
String displayPrice = String.format("£%.2f", price);
System.out.println(displayPrice);

output

£2.40

Trim

We can remove whitespace from the beginning and end of a string with trim().

java

String quoteWithWhitespace = "   Stay awhile and listen!   ";
String trimmedQuote = quoteWithWhitespace.trim();
System.out.println(trimmedQuote);

output

Stay awhile and listen!