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  1. import java.io.File;
  2. import java.io.FileNotFoundException;
  3. import java.io.PrintWriter;
  4. import java.text.DecimalFormat;
  5.  
  6. public class Main {
  7.  
  8. 	public static void main(String[] args) {
  9. 		int n = 1000000;
  10. 		double[] a = new double[n];
  11. 		for(int i=0;i<n;i++) {
  12. 			a[i] = Math.random();
  13. 		}
  14. //		format1(n,a);
  15. //		format2(n,a);
  16. //		format3(n,a);
  17. 		format4(n,a);
  18. 	}
  19.  
  20. 	public static void format1(int n,double[] a) {
  21. 		try {
  22. 			PrintWriter pw = new PrintWriter(new File("out1.txt"));
  23. 			long stime = System.nanoTime();
  24. 			for(int i=0;i<n;i++) {
  25. 				pw.printf("%.7f\n", a[i]);
  26. 			}
  27. 			pw.flush();
  28. 			pw.close();
  29. 			System.out.println((System.nanoTime() - stime) / 1000000 + " ms");
  30. 		} catch (FileNotFoundException e) {
  31. 			e.printStackTrace();
  32. 		}
  33. 	}
  34.  
  35. 	public static void format2(int n,double[] a) {
  36. 		try {
  37. 			PrintWriter pw = new PrintWriter(new File("out2.txt"));
  38. 			long stime = System.nanoTime();
  39. 			for(int i=0;i<n;i++) {
  40. 				pw.println(String.format("%.7f", a[i]));
  41. 			}
  42. 			pw.flush();
  43. 			pw.close();
  44. 			System.out.println((System.nanoTime() - stime) / 1000000 + " ms");
  45. 		} catch (FileNotFoundException e) {
  46. 			e.printStackTrace();
  47. 		}
  48. 	}
  49.  
  50. 	public static void format3(int n,double[] a) {
  51.  
  52. 		DecimalFormat df = new DecimalFormat("0.0000000");
  53. 		try {
  54. 			PrintWriter pw = new PrintWriter(new File("out3.txt"));
  55. 			long stime = System.nanoTime();
  56. 			for(int i=0;i<n;i++) {
  57. 				pw.printf(df.format(a[i]));
  58. 			}
  59. 			pw.flush();
  60. 			pw.close();
  61. 			System.out.println((System.nanoTime() - stime) / 1000000 + " ms");
  62. 		} catch (FileNotFoundException e) {
  63. 			e.printStackTrace();
  64. 		}
  65. 	}
  66.  
  67. 	public static void format4(int n,double[] a) {
  68. 		try {
  69. 			PrintWriter pw = new PrintWriter(new File("out4.txt"));
  70. 			long stime = System.nanoTime();
  71. 			for(int i=0;i<n;i++) {
  72. 				pw.printf(dtos(a[i],7));
  73. 			}
  74. 			pw.flush();
  75. 			pw.close();
  76. 			System.out.println((System.nanoTime() - stime) / 1000000 + " ms");
  77. 		} catch (FileNotFoundException e) {
  78. 			e.printStackTrace();
  79. 		}
  80. 	}
  81.  
  82. 	// http://q...content-available-to-author-only...a.com/p_shiki37/items/65c18f88f4d24b2c528b#comment-0b10eebdffb1991f3eb9
  83. 	public static String dtos(double x, int n) {
  84. 		StringBuilder sb = new StringBuilder();
  85. 		if (x < 0) {
  86. 			sb.append('-');
  87. 			x = -x;
  88. 		}
  89. 		x += Math.pow(10, -n) / 2;
  90. 		// if(x < 0){ x = 0; }
  91. 		sb.append((long) x);
  92. 		sb.append(".");
  93. 		x -= (long) x;
  94. 		for (int i = 0; i < n; i++) {
  95. 			x *= 10;
  96. 			sb.append((int) x);
  97. 			x -= (int) x;
  98. 		}
  99. 		return sb.toString();
  100. 	}
  101. }
  102.  
Success #stdin #stdout #stderr 0.17s 320576KB
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Standard input is empty
stdout
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Standard output is empty
stderr
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java.io.FileNotFoundException: out4.txt (Permission denied)
	at java.io.FileOutputStream.open0(Native Method)
	at java.io.FileOutputStream.open(FileOutputStream.java:270)
	at java.io.FileOutputStream.<init>(FileOutputStream.java:213)
	at java.io.FileOutputStream.<init>(FileOutputStream.java:162)
	at java.io.PrintWriter.<init>(PrintWriter.java:263)
	at Main.format4(Main.java:69)
	at Main.main(Main.java:17)
https://ideone.com/uRElnn
language:
Java (HotSpot 12)
created:
8 years ago
visibility:
secret

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