String.format("Hallo%n") inserts an operating system specific line break. The result differs depending on the operating system on which your program is running.
String.format("Hallo\n") always inserts a Linux line break regardless of the operating system.
String output;
// replace one placeholder
output = String.format("Hello %s", "Alex");
System.out.println(output); // Hello Alex
// replace multiple placeholders of different types
output = String.format("The %s costs $%f", "Bag", 12.99f);
System.out.println(output); // The Bag costs $12.990000
// format number to two-decimal places
output = String.format("The %s costs $%.2f", "Bag", 12.99f);
System.out.println(output); // The Bag costs $12.99
// add comma number separator
output = String.format("The %s costs $%,.2f", "Car", 54999.99f);
System.out.println(output); // The Car costs $54,999.99
// Enclose a negative numbers with parenthesis
output = String.format("Absolute zero is %(.2f degrees Celsius", -273.15f);
System.out.println(output); // Absolute zero is (273.15) degrees Celsius
// Positive/negative numbers
output = String.format("Temperature of the Sun %,+d K", 5778);
System.out.println(output); // Temperature of the Sun +5,778 K
output = String.format("Temperature of Jupiter %,+d K", -145);
System.out.println(output); // Temperature of Jupiter -145 K
// A padded number
output = String.format("A padded number %010d", 42);
System.out.println(output); // A padded number 0000000042
// A left-justified number
output = String.format("A left-justified number <%-10d>", 42);
System.out.println(output); // A left-justified number <42 >
// A right-justified number
output = String.format("A right-justified number <%10d>", 42);
System.out.println(output); // A right-justified number < 42>
// Octal numbers
output = String.format("An octal number %o", 100);
System.out.println(output);// An octal number 144
output = String.format("An octal number %#o", 100);
System.out.println(output);// An octal number 0144
// Hexadecimal numbers
output = String.format("An hex number %x", 100);
System.out.println(output); // An hex number 64
output = String.format("An hex number %#x", 100);
System.out.println(output); // An hex number 0x64
// Multiple String arguments of multiple types
output = String.format("The %1s has %2d moons", "Saturn", 53);
System.out.println(output); // The Saturn has 53 moons
// Specify a width
output = String.format("Fun with <%10s>", "Java");
System.out.println(output); //Fun with < Java>
// Specify a left justification with width
output = String.format("Fun with <%-10s>", "Java");
System.out.println(output); // Fun with <Java >
// Truncate the maximum number of characters
output = String.format("Fun with <%.1s>", "Java");
System.out.println(output); // Fun with <J>
}