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  1. import java.util.regex.Pattern;
  2.  
  3. class Test {
  4.   private Pattern pattern;
  5.   private boolean[] table;
  6.  
  7.   public boolean matches1(String a) {
  8.     return pattern.matcher(a).matches();
  9.   }
  10.  
  11.   public boolean matches2(String a) {
  12.     int length = a.length();
  13.     for (int i = 0; i < length; ++i)
  14.       if (!this.table[a.charAt(i)]) return false;
  15.     return true;
  16.   }
  17.  
  18.   public Test() {
  19.     String chars = "adhst32pomnbqf51kczyx94";
  20.     this.pattern = Pattern.compile(String.format("[%s]*", chars));
  21.     this.table = new boolean[256];
  22.     for (int i = 0; i < chars.length(); ++i)
  23.       this.table[chars.charAt(i)] = true;
  24.   }
  25.  
  26.   public static void main(String[] args) {
  27.     boolean matches;
  28.     Test test = new Test();
  29.  
  30.     long start;
  31.  
  32.     System.out.println("Regex\n=========================");
  33.     start = System.currentTimeMillis();
  34.     // best case
  35.     for (int i = 0; i < 100000; ++i)
  36.       if (test.matches1("egijlruvw0678"))
  37.         System.out.println("error!");
  38.  
  39.     System.out.printf("Time 1: %d\n", (System.currentTimeMillis() - start));
  40.     start = System.currentTimeMillis();
  41.  
  42.     // worst case
  43.     for (int i = 0; i < 1000000; ++i)
  44.       if (!test.matches1("st32pomnbqf51kczyx9"))
  45.         System.out.println("error!");
  46.  
  47.     System.out.printf("Time 2: %d\n", (System.currentTimeMillis() - start));
  48.     start = System.currentTimeMillis();
  49.  
  50.     // average case
  51.     for (int i = 0; i < 1000000; ++i)
  52.       if (!test.matches1("st32pomnbq2"))
  53.         System.out.println("error!");
  54.  
  55.     System.out.printf("Time 3: %d\n", (System.currentTimeMillis() - start));
  56.  
  57.     System.out.println("Lookup table\n=========================");
  58.     start = System.currentTimeMillis();
  59.     // best case
  60.     for (int i = 0; i < 100000; ++i)
  61.       if (test.matches2("egijlruvw0678"))
  62.         System.out.println("error!");
  63.  
  64.     System.out.printf("Time 1: %d\n", (System.currentTimeMillis() - start));
  65.     start = System.currentTimeMillis();
  66.  
  67.     // worst case
  68.     for (int i = 0; i < 1000000; ++i)
  69.       if (!test.matches2("st32pomnbqf51kczyx9"))
  70.         System.out.println("error!");
  71.  
  72.     System.out.printf("Time 2: %d\n", (System.currentTimeMillis() - start));
  73.     start = System.currentTimeMillis();
  74.  
  75.     // average case
  76.     for (int i = 0; i < 1000000; ++i)
  77.       if (!test.matches2("st32pomnbq2"))
  78.         System.out.println("error!");
  79.  
  80.     System.out.printf("Time 3: %d\n", (System.currentTimeMillis() - start));
  81.   }
  82. }
  83.  
Success #stdin #stdout 2.08s 212864KB
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stdin
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Standard input is empty
stdout
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Regex
=========================
Time 1: 43
Time 2: 985
Time 3: 690
Lookup table
=========================
Time 1: 1
Time 2: 178
Time 3: 115
https://ideone.com/oPKYq
language:
Java (HotSpot 12)
created:
12 years ago
visibility:
public

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