In Java how can I determine if a char array contains a particular character

Question

Here s what I have   char   charArray   new char     h   e   l   l   o      I want to write something to the effect of   if  charArray contains  q         break      I realize that  contains   can t be used here  I am just using  contains  to illustrate what I m trying to do

User · Answer

Some other options if you do not want your own "Utils"-class:

Use Apache commons lang (ArrayUtils):

@Test
public void arrayCommonLang(){
    char[] test = {'h', 'e', 'l', 'l', 'o'};
    Assert.assertTrue(ArrayUtils.contains(test, 'o'));
    Assert.assertFalse(ArrayUtils.contains(test, 'p'));
}

Or use the builtin Arrays:

@Test
public void arrayTest(){
    char[] test = {'h', 'e', 'l', 'l', 'o'};
    Assert.assertTrue(Arrays.binarySearch(test, 'o') >= 0);
    Assert.assertTrue(Arrays.binarySearch(test, 'p') < 0);
}

Or use the Chars class from Google Guava:

@Test
public void testGuava(){
    char[] test = {'h', 'e', 'l', 'l', 'o'};
    Assert.assertTrue(Chars.contains(test, 'o'));
    Assert.assertFalse(Chars.contains(test, 'p'));
}

Slightly off-topic, the Chars class allows to find a subarray in an array.

User · Answer

Here s a variation of Oscar s first version that doesn t use a for-each loop   for  int i   0  i  lt  charArray length  i          if  charArray i      q                do something         break            You could have a boolean variable that gets set to false before the loop  then make  do something  set the variable to true  which you could test for after the loop  The loop could also be wrapped in a function call then just use  return true  instead of the break  and add a  return false  statement after the for loop

User · Answer

You can iterate through the array or you can convert it to a String and use indexOf   if  new String charArray  indexOf  q    lt  0        break      Creating a new String is a bit wasteful  but it s probably the tersest code  You can also write a method to imitate the effect without incurring the overhead

User · Answer

This method does the trick    boolean contains char c  char   array        for  char x   array            if  x    c                return true                      return false        Example of usage   class Main        static boolean contains char c  char   array            for  char x   array                if  x    c                    return true                                  return false             public static void main String   a            char   charArray   new char     h   e   l   l   o            if   contains  q   charArray                    Do something                System out println  Hello world                            Alternative way   if   String valueOf charArray  contains  q             do something

User · Answer

From NumberKeyListener source code  This method they use to check if char is contained in defined array of accepted characters   protected static boolean ok char   accept  char c        for  int i   accept length - 1  i  gt   0  i--            if  accept i     c                return true                       return false      It is similar to    scarL  pez solution  Might be a bit faster cause of absence of foreach iterator

User · Answer

You can also define these chars as list of string  Then you can check if the characters is valid for accepted characters with list Contains x  method

User · Answer

The following snippets test for the  not contains  condition  as exemplified in the sample pseudocode in the question  For a direct solution with explicit looping  do this   boolean contains   false  for  char c   charArray        if  c     q             contains   true          break          if   contains           do something     Another alternative  using the fact that String provides a contains   method   if    new String charArray  contains  q              do something     Yet another option  this time using indexOf     if  new String charArray  indexOf  q      -1           do something

[java] In Java, how can I determine if a char array contains a particular character?

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