English | 简体中文 | 繁體中文 | Русский язык | Français | Español | Português | Deutsch | 日本語 | 한국어 | Italiano | بالعربية

Java Basic Tutorial

Java Flow Control

Java Array

Java Object-Oriented(I)

Java Object-Oriented(II)

Java Object-Oriented(III)

Java Exception Handling

Java List(List)

Java Queue(Queue)

Java Map Collection

Java Set Collection

Java Input Output (I)/O)

Java Reader/Writer

Java Other Topics

Java String format() Usage and Example

Java String (String) Methods

The Java String format() method returns a formatted string based on the parameters passed.

The syntax of the String format() method is:

String.format(String format, Object... args)

Note:

  • format() is a static method. We use the class name String to call the format() method.

  • In the above code, ... indicates that multiple objects can be passed to format().

format() parameters

  • format - Format string

  • args - 0 or more parameters

format() return value

  • Returns the formatted string

Example1: Java String format()

class Main {
　　public static void main(String[] args) {
　　　　String language = "Java";
　　　　int number =　30;
　　　　String result;
　　　　//　Format an object as a string
　　　　result = String.format("Language: %s", language);
　　　　System.out.println(result);　//　Language: Java
　　　　//Format the number as a hexadecimal number
　　　　result = String.format("Hexadecimal number: %x", number);　//　1e
　　　　System.out.println(result);　//　Hexadecimal number:　1e
　　}
}

In the above program, note the code

result = String.format("Language: %s", language);

This "Language: %s" is aFormat string.

Replace %s in the format string with the content of language. %s is a format specifier.

Similarly, %x is replaced with the hexadecimal value of number in String.format("Number: %x", number).

Format specifier

The following are commonly used format specifiers:

SpecifierDescription
%b, %BAccording to the parameter as "true" or "false"
%s, %SA string
%c, %CUnicode character
%dDecimal integer (only for integers)
%oOctal integer (only for integers)
%x, %XHexadecimal integer (only for integers)
%e, %EUsed for scientific notation (used for floating-point numbers)
%fUsed for decimal numbers (used for floating-point numbers)

Example2The string format of a number

class Main {
　　public static void main(String[] args) {
　　　　int n1　=　47;
　　　　float n2　=　35.864f;
　　　　double n3　=　44534345.76d;
　　　　//Formatted as octal digits
　　　　System.out.println(String.format("1In octal: %o", n1));　　//　57
　　　　//Formatted as hexadecimal digits
　　　　System.out.println(String.format("1In hexadecimal: %x", n1));　　//　2f
　　　　System.out.println(String.format("1In hexadecimal: %X", n1));　　//　2F
　　　　//Formatted as a string
　　　　System.out.println(String.format("1As a string: %s", n1));　　//　47
　　　　System.out.println(String.format("2As a string: %s", n2));　　//　35.864
　　　　//Scientific notation format
　　　　System.out.println(String.format("3Scientific notation: %g", n3));　//　4.45343e+07
　　}
}

Output Result

n1Octal:　57
n1Hexadecimal:　2f
n1Hexadecimal:　2F
n1As a string:　47
n2As a string:　35.864
n3Scientific notation:　4.45343e+07

You can use multiple format specifiers in the format string.

Example3: Using multiple format specifiers

//Using multiple format specifiers
//Format string
class Main {
　　public static void main(String[] args) {
　　　　int n1　=　47;
　　　　String text = "Result";
　　　　System.out.println(String.format("%s\nHexadecimal:　%x", text, n1));
　　}
}

Output Result

Result
Hexadecimal:　2f

Here, %%s is replaced with the value of text. Similarly, %%o is replaced with n1The hexadecimal value.

How Java String format() works

Example4: The format of decimal numbers

class Main {
　　public static void main(String[] args) {
　　　　float n1　=　-452.534f;
　　　　double n2　=　-345.766d;
　　　　//Format the floating-point number as is
　　　　System.out.println(String.format("1　=%f", n1));　//　-452.533997
　　　　System.out.println(String.format("2　=%f", n2));　//　-345.766000
　　　　//Display to two decimal places
　　　　System.out.println(String.format("1　=%.2f", n1));　//　-452.53
　　　　System.out.println(String.format("2　=%.2f", n2));　//　-345.77
　　}
}

Output Result

n1　=　-452.533997
n2　=　-345.766000
n1　=　-452.53
n2　=　-345.77

Note:When we use %f to format-452.534When-452.533997. This is not because the format() method. Java does not return the exact representation of floating-point numbers.

Use %%.2When the f format specifier is used, format() gives two digits after the decimal point.

Example5: Fill the number with spaces and 0

//　using more than one format specifiers
//　in a format string
class Main {
　　public static void main(String[] args) {
　　　　int n1　=　46, n2　=　-46;
　　　　String result;
　　　　　　　　//Fill the number with spaces
　　　　　　　　//The length of the string is5
　　　　result = String.format("|%5d|", n1);　//　|　　　46|
　　　　System.out.println(result);
　　　　　　　　//Fill the number with digits 0
　　　　　　　　//The length of the string is5
　　　　result = String.format("|%5d|", n1);　//　|00046|
　　　　System.out.println(result);
　　　　//Use a sign before the number
　　　　result = String.format("%+d", n1);　//　+46
　　　　System.out.println(result);
　　　　result = String.format("%+d", n2);　//　-46
　　　　System.out.println(result);
　　　　　　　　//Enclose negative numbers in parentheses
　　　　　　　　//and remove the sign
　　　　result = String.format("%(d", n2);　//　(46)
　　　　System.out.println(result);
　　}
}

Example6: Use 0x and 0 before hexadecimal and octal

//Use 0x before hexadecimal
//Use 0 before octal
class Main {
　　public static void main(String[] args) {
　　　　int n =　46;
　　　　System.out.println(String.format("%#o", n));　//　056
　　　　System.out.println(String.format("%#x", n));　//　0x2e
　　}
}

Java String format() with a language environment

If a specific language environment must be used, the String format() method also has another syntax.

String.format(Locale l, String format, Object... args)

Example7: Use GERMAN locale in format()

//Use Locale
import java.util.Locale;
class Main {
　　public static void main(String[] args) {
　　　　int number =　8652145;
　　　　String result;
　　　　//Use the current locale
　　　　result = String.format("Numbers: %,d", number);
　　　　System.out.println(result);
　　　　//Use GERMAN locale as the first parameter
　　　　result = String.format(Locale.GERMAN, "German Numbers: %,d", number);
　　　　System.out.println(result);
　　}
}

Output Result

Numbers:　8,652,145
German Numbers:　8.652.145

Note:In Germany, integers are represented by a period instead of a comma.

Java String (String) Methods

Java Method OverloadingComprehensive Java String Methods