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Problem :

I am getting bellow error
java.util.illegalformatconversionexception: d != java.lang.double

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6,930 points

2 Answers

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Solution :

You must have got a format specifier in the wrong section of the printf statement. So it needs to be in the String that is part of the first parameter, before the comma that separates method parameters. 

So not this:

System.out.printf("x = "+x+", y = %d", y);//incorrect

but rather this:

System.out.printf("x = %d, y = %d", x, y);//correct

or for new line:

System.out.printf("x = %d, y = %d%n", x, y); 

Please note in a printf or String.format(...) statement, use %n not \n for new-lines.

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This error occurs when your format specifier is wrong in printf statement. Java.util.Formatter is an interpreter for getting the C language printf style formatted strings. In java we usually use two methods to format console output which internally uses Formatter class:

System.out.prinf(String format, Object… args)

System.out.printf(Locale 1, String format, Object… args)

The format method usually consists of one or multiple formatting specifiers. A formatting specifier starts with % which is a way to specify various formatting attributes to get the desired results.

f- float/double formatting:

System.out.printf("%f%n", 1.33f);

 System.out.printf("%f%n", 1.33d);

 System.out.printf("%f%n", Double.valueOf(1.33d));

 System.out.printf("%f%n", BigDecimal.valueOf(1.33d));






Applying precision:

Syntax: x.y, where x is the width also called padding, and y is the decimal places. The value of x is ignored if it is smaller than the necessary chars including the decimal values to display. Remember x is not the limited width but to add the padding. Y is used to increase or decrease the decimal places.

System.out.printf("[%4.2f]%n", 12.34567);

 System.out.printf("[%5.2f]%n", 12.34567);

 System.out.printf("[%6.2f]%n", 12.34567);

 System.out.printf("[%7.2f]%n", 12.34567);

 System.out.printf("[%-7.2f]%n", 12.34567);

 System.out.printf("[%7.4f]%n", 12.3);

 System.out.printf("[%8.4f]%n", 12.3);




 [ 12.35]

 [  12.35]

 [12.35  ]


 [ 12.3000]

Display decimal with # flag:

The integer portion of the results always ends with a decimal point, even if the fractional part is zero.


System.out.printf("[%#1.0f]%n", 1234d);

 System.out.printf("[%1.0f]%n", 1234d);





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