How to format strings in Java

Question

Primitive question  but how do I format strings like this       Step  1  of  2     by substituting variables using Java  In C  it s easy

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Take a look at String format  Note  however  that it takes format specifiers similar to those of C s printf family of functions -- for example   String format  Hello  s   d    world   42     Would return  Hello world  42   You may find this helpful when learning about the format specifiers  Andy Thomas-Cramer was kind enough to leave this link in a comment below  which appears to point to the official spec  The most commonly used ones are     s - insert a string  d - insert a signed integer  decimal   f - insert a real number  standard notation   This is radically different from C   which uses positional references with an optional format specifier  That means that you can t do things like   String format  The  0  is repeated again   0     word          without actually repeating the parameter passed to printf format   see  The Scrum Meister s comment below     If you just want to print the result directly  you may find System out printf  PrintStream printf  to your liking

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Java 15 There is a new instance method called String  formatted Object    args  as of Java 15  The internal implementation is same to String  format String format  Object    args    Formats using this string as the format string  and the supplied arguments   String step1    quot one quot   String step2    quot two quot       results in  quot Step one of two quot  String string    quot Step  s of  s quot  formatted step1  step2         Advantage  The difference is that the method is not static and the formatting pattern is a string itself from which a new one is created based on the args  This allows chaining to build the format itself first  Disadvantage  There is no overloaded method with Locale  therefore uses the default one  If you need to use a custom Locale  you have to stick with String  format Locale l String format Object    args

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I wrote this function it does just the right thing  Interpolate a word starting with   with the value of the variable of the same name   private static String interpol1 String x       Field   ffield    Main class getDeclaredFields        String   test   x split            for  String v   test             for   Field n  ffield                 if v startsWith       amp  amp    n getName   equals v substring 1                        try                       x   x replace       v substring 1   String valueOf  n get null                      catch  Exception e                       System out println                                                          return x

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I ve wrote my simple method for it     public class SomeCommons           Message Format like  Some String  0     1   with arguments        public static String msgFormat String s  Object    args            return new MessageFormat s  format args             so you can use it as    SomeCommons msfgFormat  Step  1  of  2    1    two

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In addition to String format  also take a look java text MessageFormat   The format less terse and a bit closer to the C  example you ve provided and you can use it for parsing as well   For example       int someNumber   42  String someString    foobar   Object   args    new Long someNumber   someString   MessageFormat fmt   new MessageFormat  String is    1     number is  0      System out println fmt format args      A nicer example takes advantage of the varargs and autoboxing improvements in Java 1 5 and turns the above into a one-liner   MessageFormat format  String is    1     number is  0     42   foobar      MessageFormat is a little bit nicer for doing i18nized plurals with the choice modifier   To specify a message that correctly uses the singular form when a variable is 1 and plural otherwise  you can do something like this   String formatString    there were  0   0 choice 0 objects 1 object 1 lt objects    MessageFormat fmt   new MessageFormat formatString   fmt format new Object     new Long numberOfObjects

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public class StringFormat        public static void main String   args                Scanner sc new Scanner System in               System out println                                                  for int i 0 i lt 3 i                     String s1 sc next                    int x sc nextInt                    System out println String format   -15s 03d  s1 x                              System out println                                                    outpot                                        ved15space123   ved15space123   ved15space123                                       Java solution   The  -  is used to left indent The  15  makes the String s minimum length it takes up be 15 The  s   which is a few characters after    will be substituted by our String The 0 pads our integer with 0s on the left The 3 makes our integer be a minimum length of 3

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If you choose not to use String format  the other option is the   binary operator  String str    Step     a     of     b    This is the equivalent of  new StringBuilder  Step    append String valueOf 1   append   of    append String valueOf 2     Whichever you use is your choice  StringBuilder is faster  but the speed difference is marginal  I prefer to use the   operator  which does a StringBuilder append String valueOf X    and find it easier to read

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This solution worked for me  I needed to create urls for a REST client dynamically so I created this method  so you just have to pass the restURL like this   customer  0  user  1  order   and add as many params as you need   public String createURL  String restURL  Object     params               return new MessageFormat restURL  format params       You just have to call this method like this   createURL   customer  0  user  1  order   123  321     The output        customer 123 user 321 order

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The org apache commons text StringSubstitutor helper class from Apache Commons Text provides named variable substitution Map lt String  String gt  valuesMap   new HashMap lt  gt     valuesMap put  quot animal quot    quot quick brown fox quot    valuesMap put  quot target quot    quot lazy dog quot    String resolved   new StringSubstitutor valuesMap  replace  quot The   animal  jumped over the   target   quot    System out println resolved      The quick brown fox jumped over the lazy dog

[java] How to format strings in Java

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