How to print a number into specific length of space in Java?-CodePudding

I want to print a fractional number into specific length of space with formatting, in Java. But the length will defined while algorithm running, so I can't use straight formatting, such as:

System.out.printf("%8.1f)

For example that lenght "8" will defined somewhere else while code running, how can I configure it to make it automatic depends on code?

CodePudding user response：

Simply build the string with concatenation

int x = 8;
System.out.printf("%"   x   ".1f\n", 1.123);

CodePudding user response：

Try this, where your formatting is determined by some 'length' defined in the code:

double x = 5.2375484914759291;
int length = 8;
String format = "%." length "f";
System.out.printf(format,x);
//5.23754849 is the output for printf("%.8f",5.2375484914759291)

By concatenating formatting strings to your number variable, you can specify the formatting. Here is an example of formatting the width for an int:

int y = 247;
int width = 8;
String formatWidth ="%0"   width   "d";
System.out.printf(formatWidth,y);
//00000247 is the output for printf("d",247)

Extending this to format both length and width:

double z = 247.7526;
int length = 2;
int width = 8;
String formatBoth = "%0"   width   "."   length   "f";
System.out.printf(formatBoth,z);
//00247.75 is the output for printf(".2f",247.7526)

You could also play around with your formatting string by declaring length and width as String variables, depending on your code.