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  1.  
  2. class KusoString {
  3.     public KusoString(String text) {
  4. 		this.text = text;
  5. 		this.hashValue = this.hashCode();
  6. 	}
  7.  
  8. 	private final int hashValue;
  9. 	private final String text;
  10.  
  11. 	@Override
  12. 	public boolean equals(Object arg0) {
  13. 		if ( arg0 == null || !(arg0 instanceof KusoString) )
  14. 			return false;
  15. 		KusoString other = (KusoString)arg0;
  16.  
  17. 		if ( this.hashValue != 0 && other.hashValue != 0 && this.hashValue != other.hashValue )
  18. 			return false;
  19.  
  20. 		if ( this.text == null && other.text == null )
  21. 			return true;
  22. 		if ( this.text == null && other.text != null )
  23. 			return false;
  24. 		if ( this.text != null && other.text == null )
  25. 			return false;
  26.  
  27. 		assert this.text != null && other.text != null;
  28. 		if ( this.text.length() != other.text.length() )
  29. 			return false;
  30.  
  31. 		for ( int i = 0; i < this.text.length(); i++ ) {
  32. 			if ( this.text.charAt(i) != other.text.charAt(i) )
  33. 				return false;
  34. 		}
  35.  
  36. 		return true;
  37. 	}
  38.  
  39. 	@Override
  40. 	public int hashCode() {
  41. 		return this.text.hashCode();
  42. 	}
  43. }
  44.  
  45. class Program {
  46. 	public static void main(String[] args) throws Exception {
  47. 		StringBuilder sb = new StringBuilder();
  48. 		for ( int i = 0; i < 256 * 1024; i++ )
  49. 			sb.append('a');
  50. 		KusoString t1 = new KusoString(sb.toString() + '1');
  51. 		KusoString t2 = new KusoString(sb.toString() + '1');
  52. 		KusoString t3 = new KusoString(sb.toString() + '2');
  53. 		System.out.printf("%s\n", t1.equals(t2));
  54.  
  55. 		System.out.printf("ちょっとテスト\n");
  56. 		test(t1, t2);
  57.  
  58. 		System.out.printf("全比較したとき\n");
  59. 		test(t1, t2);
  60. 		System.out.printf("ハッシュ比較で済んだとき\n");
  61. 		test(t1, t3);
  62. 	}
  63.  
  64. 	private static void test(KusoString t1, KusoString t2) {
  65. 		final int N = 1000 * 1;
  66. 		long ts = System.currentTimeMillis();
  67.  
  68. 		boolean b = false;
  69. 		for ( int i = 0; i < N; i++ )
  70. 			b |= t1.equals(t2);
  71.  
  72. 		long te = System.currentTimeMillis();
  73. 		System.out.printf("    %.1fus\n", (double)(te - ts) / N * 1000, b);
  74. 	}
  75. }
  76.  
  77.  
Success #stdin #stdout 2.07s 380352KB
comments (?)
stdin
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Standard input is empty
stdout
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true
ちょっとテスト
    980.0us
全比較したとき
    979.0us
ハッシュ比較で済んだとき
    0.0us
https://ideone.com/t4oYJq
language:
Java (12.0.1)
created:
10 years ago
visibility:
secret

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