Java printf标志顺序

Question

在printf中使用标志时，我需要遵循什么特定顺序吗？

1.System.out.printf("%+04d + %s ", 12, "a");// include sign then pad zeros      
2.System.out.printf("\n%04+d + %s ", 12, "a");// pad zeros then include sign    
3.System.out.printf("\n%+-4d + %s ", 12, "a");// include sign then left justify 
4.System.out.printf("\n%-4+d + %s ", 12, "a");// left justify then include sign 


The answer is: 

+012 + a 
Exception in thread "main" java.util.UnknownFormatConversionException: Conversion = '0'
+12  + a 
Exception in thread "main" java.util.UnknownFormatConversionException: Conversion = '-'     

谢谢。

Answer 1

是顺序问题，这就是为什么您会因某些组合而异常：

% [flags][width][.precision] conversion-character (square brackets denote optional parameters)

谢谢