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Java String.format Method

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The Java String.format method is one of the Java String Method which is used to return a formatted string using the user specified format and arguments.

In this article we will show you, How to write Java String format method with example. Before we get into the example, let us see the basic syntax of the string.format in Java Programming language is as shown below.

Java String.format syntax

The Java Programming Language provides two different methods to format the given string. Following method accepts two parameters: first parameter is the format you want to apply, and second is the arguments referenced by the format specifier.

public static String format (String format, Object.. args);  // It will return String as output 

//In order to use in program
String.format (String format, Object.. args);

The following string.format java method accepts three parameters: first parameter is the locale you want to apply, second parameter is the format you want to apply. The third argument is the arguments referenced by the format specifier.

public static String format (locale l, String format, Object.. args);  // It will return String as output 

//In order to use in program
String.format (locale l, String format, Object.. args);
  • Locale: This is the locale you want to apply during the formatting. If the locale is NULL then no localization is applied.
  • Format: Please specify the format string. For example, %d, %f, %s etc.
  • Args: Arguments referenced by the format specifier in Format. If we specify more arguments than the format specifier, the extra arguments will be ignored.

TIP: If you omit Locale argument then String.format in Java will take the system default localization.

Throws

IllegalFormatException: If the format string contains any illegal syntax then format method will throw this error. Illegal syntax may include:

  • When the format specifier is incompatible with the given arguments.
  • If we specify insufficient arguments.

NullPointerException: If the format is NULL.

Java String.format Example

The Java String.format method is used to format the given object using the user specified format. In this Java program, We are going to the same.

JAVA CODE

// Java String format method example
package StringFunctions;
import java.util.Date;
import java.util.Locale;

public class FormatMethod {

	public static void main(String[] args) {
		double dbl = 98765.457896;
		
		String str1 = String.format("%f", dbl);
		System.out.println(str1);
		
		String str2 = String.format("%,2.4f", dbl);
		System.out.println(str2);
		
		String str3 = String.format("%d", 9876);
		System.out.println(str3);
		
		String str4 = String.format("-%d", 2406);
		System.out.println(str4);
		
		String str5 = String.format("Today is %tD", new Date());
		System.out.println(str5);
		
		String str6 = String.format("%s", 240.9876);
		System.out.println(str6);
		
		String str = "Tutorial";
		String std = String.format(Locale.ENGLISH, "%s Gateway",str);
		System.out.println(std);
	}
}

OUTPUT

Java String.format Method 1

ANALYSIS

Within this example program, First we declared a double variables dbl and assigned some random value using following statement

double dbl = 98765.457896;

Following string.format java statement will call the public static String format (String format, Object.. args) method to format the user specified double value to float.

String str1 = String.format("%f", dbl);

The following format statement will format 9876 value to positive integer.

String str3 = String.format("%d", 9876);

Below statement will format 2406 value to Negative integer.

String str4 = String.format("-%d", 2406);

Following java string.format statement will format 240.9876 value to String data.

String str6 = String.format("%s", 240.9876);

The following statement will call the public static String format (locale l, String format, Object.. args) method to format the string data using user specified local (i.e., ENGLISH) here.

String std = String.format(Locale.ENGLISH, "%s Gateway",str);

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