Simple Java programming illustrated

Simple java programming is shown in the figure. How to change the output result to retain three digits

printf("s=%.3f",s); keep 3 decimal places

Look at the following examples:

double d = 345.678;

String s = "hello!";

int i = 1234;

//"%" means formatted output, and the content after "%" is the definition of the format.

System.out.printf("%f",d);//"f" means formatted output floating point number.

System.out.printf("%9.2f",d);//The 9 in "9.2" represents the length of the output, and 2 represents the number of digits after the decimal point.

System.out.printf(＂% 9.2f＂,d); //"＂" indicates that the output number has a positive or negative sign.

System.out.printf("%-9.4f",d); //"-" means the output number is left-aligned (default is right-aligned).

System.out.printf("% -9.3f",d); //"-" indicates that the output number is signed and left-aligned.

System.out.printf("%d",i);//"d" means output decimal integer.

System.out.printf("%o",i);//"o" means outputting an octal integer.

System.out.printf("%x",i);//"d" means outputting a hexadecimal integer.

System.out.printf("%#x",i);//"d" means outputting an integer with hexadecimal flag.

System.out.printf("%s",s);//"d" represents the output string.

System.out.printf ("Output a floating point number: %f, an integer: %d, a string: %s", d, i, s); // Multiple variables can be output, pay attention to the order.

System.out.printf ("String: %2$s, hexadecimal number of %1$d: %1$#x", i, s); // "X$" represents the number variables.

Java programming: Enter the radius of the ball and calculate the volume of the ball to three decimal places

just for reference:

/*

*It is known that the volume of the sphere is 4/3πr3. Try writing a program that inputs the radius of the sphere and calculates the volume of the sphere.

*Enter

from the command window

*/

import java.util.Scanner;

public class Volume{ //Define class member variables in Java

public static void main(String args[]){ //main() method body, the entrance to a java application program

Scanner s=new Scanner(System.in);

System.out.println ("Please enter the radius r of the sphere you want to volume"); //Output prompt content

double r=s.nextDouble(); //Define a double variable

double v; //Define a double variable

v=4*Math.PI*Math.pow(r,3)/3; //Operation expression

System.out.println("The volume of the sphere is "v"); //Output the calculation results and output "The volume of the sphere is" at the beginning

}

}

java reserved digits issue

It is very convenient to use the classes that come with Java. Let me give you an example:

import java.text.DecimalFormat;

public class Test {

public static void main(String[] args) {

double num = 0.235463;

DecimalFormat fmt = new DecimalFormat(".

%＂");

System.out.println(fmt.format(num));

}

}

// Display: 23.546%

The # in ".

%" means it will be displayed if it is present, and it will not be displayed if it is not, so 3 #s represent it. It can be accurate to 3 digits after the decimal point at most, and the extra digits will be omitted.

How to set the number of decimal points to retain in Java calculations

method one:

rounding

double f = 111231.5585;

BigDecimal b = new BigDecimal(f);

double f1 = b.setScale(2, BigDecimal.ROUND_HALF_UP).doubleValue();

Retain two decimal places

Method 2:

java.text.DecimalFormat df =new java.text.DecimalFormat(”#.00″);

df.format (the number you want to format);

Example: new java.text.DecimalFormat(”#.00″).format(3.1415926)

#.00 means two decimal places #.0000 means four decimal places and so on...

Method 3:

double d = 3.1415926;

String result = String .format(”%.2f”);

###%.2f %. means any number of digits before the decimal point. 2 means two decimal places. The formatted result is f, which means floating point type. ###

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