Output info to the screen
- Use the System.out.print function:
System.out.print("desired text");Note that multiple statements above print on the same line.
Text in double quotes " " is known as a string literal.
System.out.println (note the ln at the end, short for "line"), starts a new output line after the outputted values, called a newline.
The syntax for outputting the double myFloat with two digits after the decimal point is
System.out.printf("%.2f", myFloat);Format specifiers for the printf() and format() methods.
| Format specifier | Data type(s) | Notes |
|---|---|---|
| %c | char | Prints a single Unicode character |
| %d | int, long, short | Prints a decimal integer value. |
| %o | int, long, short | Prints an octal integer value. |
| %h | int, char, long, short | Prints a hexadecimal integer value. |
| %f | float, double | Prints a floating-point value. |
| %e | float, double | Prints a floating-point value in scientific notation. |
| %s | String | Prints the characters in a String variable or literal. |
| %% | Prints the "%" character. | |
| %n | Prints the platform-specific new-line character. |
Floating-point formatting
%(flags)(width)(.precision)specifier| Sub-specifier | Description | Example |
|---|---|---|
| width | Specifies the minimum number of characters to print. If the formatted value has more characters than the width, the value will not be truncated. If the formatted value has fewer characters than the width, the output will be padded with spaces (or 0's if the '0' flag is specified). | printf("Value: %7.2f", myFloat); Value: 12.34 |
| .precision | Specifies the number of digits to print following the decimal point. If the precision is not specified, a default precision of 6 is used. | printf("%.4f", myFloat); 12.3400 printf("%3.4e", myFloat); 1.2340e+01 |
| flags | -: Left aligns the output given the specified width, padding the output with spaces. +: Prints a preceding + sign for positive values. Negative numbers are always printed with the - sign. 0: Pads the output with 0's when the formatted value has fewer characters than the width. space: Prints a preceding space for positive value. | printf("%+f", myFloat); +12.340000 printf("%08.2f", myFloat); 00012.34 |
Integer formatting
| Sub-specifier | Description | Example |
|---|---|---|
| width | Specifies the minimum number of characters to print. If the formatted value has more characters than the width, the value will not be truncated. If the formatted value has fewer characters than the width, the output will be padded with spaces (or 0's if the '0' flag is specified). | printf("Value: %7d", myInt); Value: 301 |
| flags | -: Left aligns the output given the specified width, padding the output with spaces. +: Print a preceding + sign for positive values. Negative numbers are always printed with the - sign. 0: Pads the output with 0's when the formatted value has fewer characters than the width. space: Prints a preceding space for positive value. | printf("%+d", myInt); +301 printf("%08d", myInt); 00000301 printf("%+08d", myInt); +0000301 |
String formatting
| Sub-specifier | Description | Example |
|---|---|---|
| width | Specifies the minimum number of characters to print. If the string has more characters than the width, the value will not be truncated. If the formatted value has fewer characters than the width, the output will be padded with spaces. | printf("%20s String", myString); Formatting String |
| .precision | Specifies the maximum number of characters to print. If the string has more characters than the precision, the string will be truncated. | printf("%.6s", myString); Format |
| flags | -: Left aligns the output given the specified width, padding the output with spaces. | printf("%-20s String", myString); Formatting String |
Flushing output
The PrintStream method flush() flushes the stream's buffer contents. Ex: The statement System.out.flush(); writes the contents of the buffer for System.out to the computer screen. Most Java implementations make System.out flush when a newline character is output or println() method is called.