In math, formatting rarely matters. \u00a0If the correct answer is 0.012, you can answer as 1.2e-2, 3\/250, or 0.01200. Most computer environments, like most calculators, give an “unformatted” answer to a calculation. Not too surprisingly, when I ask Java for the square root of 14, it gives 3.7416573867739413, which is perhaps more than sufficient.<\/p>\n
In physics, chemistry, or financial contexts, people aren’t as tolerant of unformatted answers. Scientists expect answers to correct precision. Monetary values are expected to two decimal places.<\/p>\n
Java has a class that helps the programmer to display numeric output according to any desired format: DecimalFormat. It’s invoked with a pattern that describes the desired format. An example: <\/p>\n
DecimalFormat form0 = new DecimalFormat(“#,###.00”);<\/span><\/p>\n In order to use the DecimalFormat class, you must include the line<\/p>\n import java.text.DecimalFormat;<\/span><\/p>\n above the class declaration.<\/p>\n Following is a short program that illustrates the use of Java’s DecimalFormat. (It uses the Java Scanner, about which I wrote a series starting here<\/a>.)<\/p>\n Let’s imagine you save the above program as DecFormatEx.java<\/span>, then compile it as follows:<\/p>\n javac DecFormatEx.java<\/span><\/p>\n Finally, you run it with the following command call:<\/p>\n java DecFormatEx 1139.726 23 0.113e1 2000000.29<\/span><\/p>\n You’ll hopefully receive the output As usual, this little Java program needs more explanation than fits in one post. I’ll be continuing about it tomorrow.<\/p>\n HTH:)<\/p>\n Source:<\/p>\n docs.oracle.com<\/a><\/p>\n
\nimport java.text.DecimalFormat;
\nimport java.util.Scanner;\/\/needed for the scanner<\/span>
\n
\nclass DecFormatEx{
\n\/*This class reads numbers given with the command call, then displays them formatted to two decimal places with the thousands separated by commas.*\/<\/span>
\npublic static void main(String[] args){
\n
\nDecimalFormat dec0=new DecimalFormat(“#,###.00”);
\ndouble num0;
\nString string0;
\nfor(int i=0;i
\nif(scan0.hasNextDouble()){
\nnum0=scan0.nextDouble();
\nstring0=dec0.format(num0);
\nSystem.out.println(“The number, formatted, is “+string0+”\\n”);
\n}
\nelse{
\nSystem.out.println(args[i] + ” not a readable number.\\n”);
\n}
\n}\/\/end of for loop<\/span>
\nSystem.out.println(“\\nSee you again:)\\n\\n”);
\n}\/\/end of main<\/span>
\n}\/\/end of class<\/span><\/p>\n
\n
\nThe number, formatted, is 1,139.73
\nThe number, formatted, is 23.00
\nThe number, formatted, is 1.13
\nThe number, formatted, is 2,000,000.29
\n<\/span><\/p>\n