How do I make my string comparison case insensitive

Question

I created a Java program to compare two strings   String s1    Hello   String s2    hello    if  s1 equals s2         System out println  hai      else       System out println  welcome        It displays  welcome   I understand it is case sensitive  But my problem is that I want to compare two strings without case sensitivity  I e  I expect the output to be hai

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import java lang String    contains equalsIgnoreCase           String s1    Hello   String s2    hello    if  s1 equalsIgnoreCase s2     System out println  hai      else   System out println  welcome        Now it will output   hai

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You can use equalsIgnoreCase

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The best would be using s1 equalsIgnoreCase s2    see javadoc   You can also convert them both to upper lower case and use s1 equals s2

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To be nullsafe  you can use  org apache commons lang StringUtils equalsIgnoreCase String  String    or  org apache commons lang3 StringUtils equalsIgnoreCase CharSequence  CharSequence

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String equalsIgnoreCase is the most practical choice for naive case-insensitive string comparison   However  it is good to be aware that this method does neither do full case folding nor decomposition and so cannot perform caseless matching as specified in the Unicode standard  In fact  the JDK APIs do not provide access to information about case folding character data  so this job is best delegated to a tried and tested third-party library   That library is ICU  and here is how one could implement a utility for case-insensitive string comparison   import com ibm icu text Normalizer2           public static boolean equalsIgnoreCase CharSequence s  CharSequence t        Normalizer2 normalizer   Normalizer2 getNFKCCasefoldInstance        return normalizer normalize s  equals normalizer normalize t              String brook     u u0308  chen       String BROOK    FL  SSCHEN        assert equalsIgnoreCase brook  BROOK     Naive comparison with String equalsIgnoreCase  or String equals on upper- or lowercased strings will fail even this simple test    Do note though that the predefined case folding flavour getNFKCCasefoldInstance is locale-independent  for Turkish locales a little more work involving UCharacter foldCase may be necessary

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You have to use the compareToIgnoreCase method of the String object   int compareValue   str1 compareToIgnoreCase str2     if  compareValue    0  it means str1 equals str2

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public boolean newEquals String str1  String str2        int len   str1 length    int len1   str2 length    if len  len1        for int i 0 j 0 i lt str1 length   i   j                  if str1 charAt i   str2 charAt j           return false        enter code here    return true

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In the default Java API you have   String CASE INSENSITIVE ORDER   So you do not need to rewrite a comparator if you were to use strings with Sorted data structures   String s    some text here   s equalsIgnoreCase  Some text here      Is what you want for pure equality checks in your own code   Just to further informations about anything pertaining to equality of Strings in Java  The hashCode   function of the java lang String class  is case sensitive    public int hashCode         int h   hash      if  h    0  amp  amp  value length  gt  0            char val     value           for  int i   0  i  lt  value length  i                  h   31   h   val i                     hash   h            return h      So if you want to use an Hashtable HashMap with Strings as keys  and have keys like  SomeKey    SOMEKEY  and  somekey  be seen as equal  then you will have to wrap your string in another class  you cannot extend String since it is a final class   For example    private static class HashWrap       private final String value      private final int hash       public String get             return value             private HashWrap String value            this value   value          String lc   value toLowerCase            this hash   lc hashCode                Override     public boolean equals Object o            if  this    o  return true          if  o instanceof HashWrap                HashWrap that    HashWrap  o              return value equalsIgnoreCase that value             else               return false                        Override     public int hashCode             return this hash            and then use it as such   HashMap lt HashWrap  Object gt  map   new HashMap lt HashWrap  Object gt

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More about string can be found in String Class and String Tutorials

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Use s1 equalsIgnoreCase s2   https   docs oracle com javase 1 5 0 docs api java lang String html equalsIgnoreCase java lang String

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Use String equalsIgnoreCase     Use the Java API reference to find answers like these   https   docs oracle com javase 1 5 0 docs api java lang String html equalsIgnoreCase java lang String   https   docs oracle com javase 1 5 0 docs api

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Note that you may want to do null checks on them as well prior to doing your  equals or  equalsIgnoreCase   A null String object can not call an equals method   ie   public boolean areStringsSame String str1  String str2        if  str1    null  amp  amp  str2    null          return true      if  str1    null    str2    null          return false       return str1 equalsIgnoreCase str2

[java] How do I make my string comparison case insensitive?

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