String.format metodu

Giriş

İmzası şöyle. 

public static String format(String format, Object... args) 
public static String format(Locale l, String format, Object... args) {

Söz dizimi şöyle. Her zaman % format specifier ile başlar

%<index$><flags><width><.precision><conversion>

Locale Kullanımı

Örnek

Şöyle yaparız

String name = "Tandrew";
int age = 16;

String formattedString = String.format(Locale.US, "My name is %s and I am %d years old",
  name, age);

// notice the format specifiers %s and %d
System.out.println(formattedString); 

// Output: My name is Tandrew and I am 16 years old

1. Index

Açıklaması şöyle

<index$> is an optional positive integer that corresponds to an argument in the argument list. This index starts at 1 (i.e., the first argument in the argument list is indexed as 1). Therefore, the first argument in the argument list can be addressed using 1$, the second argument can be addressed using 2$, and so on. For example, we can format a String — which has a conversion of s— that corresponds to the second argument in our argument list using the following format specifier:

Örnek

Şöyle yaparız

String.format("The hex value of %d is 0x%1$h",8756);//"The hex value of 8756 is 0x2234"

2. Flags

Flags şöyle

-            Left-justifies the results.

#           Uses an alternative form.

+           Always includes a sign.

(space) Add leading space for positive values.

0           Zero-pads the result.

,            Includes locale-specific grouping separators.

(            Encloses negative numbers in parenthesis.

3. Width

Örnek

Şöyle yaparız. 

Birinci örnekte % formatlamaya başlama karakteridir, 10 width içindir gerekirse sağa doğru doldurulur, s ise parametrenin string olarak formatlanacağını belirtir

İkinci örnekte % formatlamaya başlama karakteridir, -10 width içindir ve gerekirse sola doğru doldurulur, s ise parametrenin string olarak formatlanacağını belirtir

String formattedString1 = String.format("%10s", "name");    // Result: "name      "
String formattedString2 = String.format("%-10s", "name");   // Result: "      name"

Örnek

Şöyle yaparız.

0 baş tarafı doldurma karakteridir, 32 width içindir,  x ise parametrenin hexadecimal olarak formatlanacağını belirtir

BigInteger n = ...;
String md5h = String.format("%032x",n);

4. Precision

Açıklaması şöyle

General: 

Maximum number of characters displayed; if the supplied argument results in more characters than the supplied precision, the resulting string is truncated to the correct number of characters. For example, supplying Justin as an argument to the format specifier %.1s result in J.

Floating point (e, E, and f): 

Number of digits after the decimal place. For example, a format specifier of %.1f with an argument of 1.2345 results in 1.2.

Floating point (g, G, a and A): 

Number of digits in the magnitude after rounding.

5. Conversion Tablosu

Conversion Tablosu şöyle

%b, B : true, false, TRUE, FALSE

%h, H : fff03,6199ec4,6199EC4

%s, S : foo ,bar, BAR

%c, C : c, f ,F

%d :     10,5347

%o :      2,151

%x, X :  ff4,e56d2,E56D2

%e, E :  1.114313e+09,1.682340e-08,1.682340E-08

%f :       4.562340, 1245.643876

%g, G : 128636, 8.12935e+16,3546.50,8.12935E+16

%a, A :  0x1.63c774a3d70a4p19, 0x1.187ff0337c5abp-26, 0X1.8D7025536252DP45

Boolean %b veya %B

Açıklaması şöyle

The boolean result as a string (e.g., true or false) if the supplied argument is a Boolean. false if the supplied argument is null and true for all other arguments. If B is used, the resulting boolean value is capitalized (e.g., TRUE or FALSE).

Hexadecimal String -%h veya %h

Açıklaması şöyle. fff03, 6199ec4, 6199EC4 gibi

The hexadecimal value of the supplied argument, arg, by applying the expression Integer.toHexString(arg.hashCode()). Note that the result does not include a 0x prefix. If H is used, the resulting alphabetic hexadecimal characters are capitalized.

String - %s

Açıklaması şöyle

The provided argument as a string (by invoking Object.toString). If the supplied argument is a Formattable object, the string is obtained by invoking Formattable.formatTo. If S is supplied, the supplied string is capitalized.

Şöyle yaparız.

int a = ...;
int b = ...;
int c = ...;
return String.format("%s-%s-%s", a, b, c);

Character %c veya %C

Açıklaması şöyle

The Unicode character. If a String object is supplied, an IllegalFormatConversionException is thrown. If C is used, the supplied character is capitalized.

Integer -%d

Açıklaması şöyle

The decimal integer.

Şöyle yaparız.

String.format("%011d", 4366)

Çıktı olarak şunu alırız

00000004366

Octal Integer -%o

Açıklaması şöyle. 12, 151 gibi

The octal integer.

hexadecimal Integer - %x veya %X

Açıklaması şöyle. ff4, e56d2, E56D2 gibi

The hexadecimal integer. Note that the result does not include a 0x prefix. This specifier should be preferred over h when supplying an integer. If X is used, the resulting alphabetic hexadecimal characters are capitalized.

Şöyle yaparız.

int a = ...;
System.out.println( String.format("%X", a) );

Floating Point - %e veya %E

Açıklaması şöyle. 1.114313e+09, 1.682340e-08, 1.682340E-08 gibi

The value in scientific notation. If E is used, the exponent symbol (e) is capitalized (i.e., E).

Floating Point - %f

Açıklaması şöyle.

Use %.4f to perform the rounding you want. This format specifier indicates a floating point value with 4 digits after the decimal place. Half-up rounding is used for this, meaning that if the last digit to be considered is greater than or equal to five, it will round up and any other cases will result in rounding down.

Örnek
Şöyle yaparız.

String.format("%.2f", 62.1232131342);

Floating Point In Scientific Notation Or Decimal Format- %g

Açıklaması şöyle. 128636, 8.12935e+16, 3546.50, 8.12935E+16 gibi

The value in scientific notation or decimal format, depending on the result after rounding. If G is used, the exponent symbol (e) is capitalized (i.e., E).

Açıklaması şöyle.

The %g format specifier is used to indicate how many significant digits in scientific notation are displayed. Leading zeroes are not significant, so they are skipped.

Örnek
Şöyle yaparız. Çıktı olarak 0.1235 alırız

String.format("%.4g", 0.1234712)

Örnek
Şöyle yaparızz. Çıktı olarak 0,0009877 alırız

String.format("%.4g", 0.000987654321)

Floating Point In Scientific Notation - %a veya %A

Açıklaması şöyle.  0x1.63c774a3d70a4p19, 0x1.187ff0337c5abp-26, 0X1.8D7025536252DP45 gibi

The value in scientific notation, where the significand is a hexadecimal floating point value, and the power follows a p delimiter. If A is used, the resulting alphabetic hexadecimal characters are capitalized and the p delimiter is capitalized (i.e., P).