Java 抓取字符串中的字数和字符数

我正在尝试编写一个超级高效的方法，该方法在两种“模式”（

WORD

和

CHARACTER

）下运行，它接受字符串并告诉我其中的字数（由1+空格分隔）或字符数（非空格字符）：

我知道我可以使用

StringTokenizer

完成

WORD

模式版本：

StringTokenizer tokenizer = new StringTokenizer(" ");

但是对于

字符

模式（非空白字符的数量），我完全没有任何线索。我相信我可以用一些粗糙的东西，比如：

for(int i = 0; i < toExamine.length; i++)
    if(Character.isSpace(toExamine.charAt(i)))
        count++;

for（int i=0；i

---

但这有点难看，可能不是最有效的方法（对于

StringTokenizer

片段也是如此）。这里是否可以使用正则表达式，或者其他一些Java字符串/字符疯狂，以超高效的方式满足我的需求？我在这里研究数千万根弦。提前感谢。

转换为字符数组并使用for循环进行迭代

int charCount =0;
for(int i=0; i<sentence.length(); i++) {
    if(!Character.isWhitespace(sentence.charAt(i))) {
        charCount++;
    }
}

---

这并不比

for

循环快，但如果需要使用正则表达式，可以尝试以下方法：

int noSpaces=toExamine.split("\\s+").length-1; 

字符数为：

int noChar=toExamine.length-noSpaces;

---

下面的测试程序产生以下结果。程序将输出5组这样的结果，但我在这里只显示一组。带有

/

的行是我的注释，而不是程序的输出

// Percentage of non-space over space is approximately 0.857 // Length of the full string generated is 1 075 662 0.857 1075662 // Name_of_method (Result): 15_Runs_In_Microseconds | Average_In_Microseconds countWords_1 (131489): 20465 20240 21045 20193 20000 19972 20551 39489 19859 19971 19889 19877 20049 19900 19949 | 21429 countWords_2 (131489): 255500 258723 254543 255956 253606 263549 254096 254402 254191 254296 253752 261501 260788 261574 254178 | 256710 countWords_3 (131489): 26225 25022 24830 24829 24545 24819 25459 24625 25628 24700 24936 24794 24794 24849 25026 | 25005 countWords_4 (131489): 24537 24169 25283 24862 23863 23902 24068 23906 51472 23731 23889 23844 23832 24275 23896 | 25968 countWords_5 (131489): 81087 112095 80008 81290 81472 80581 80717 80460 79870 80557 80694 80923 145686 80564 80849 | 87123 countWords_6 (131489): 114391 114146 111946 111873 112331 167207 134117 118217 112843 112804 113533 111834 112830 112392 118181 | 118576 countChars_1 (922546): 150507 109102 150453 111352 149753 108099 153842 109034 150817 117258 149219 108194 152839 110340 149524 | 132022 countChars_2 (922546): 28779 29473 52499 27182 26519 27743 26717 27161 26451 27060 26307 27309 26350 62824 33134 | 31700 countChars_3 (922546): 25408 25127 24980 24832 24624 24671 24848 24712 24634 24622 24607 24613 24661 24765 24883 | 24799 countChars_4 (922546): 81489 82246 80906 80718 80803 81147 81113 81798 81030 81024 108508 80768 80780 80671 80753 | 82916 countChars_5 (922546): 26086 25546 24846 43734 25016 25083 24894 25530 25031 25041 25114 24935 25358 24895 43498 | 27640 countChars_6 (922546): 102559 102257 101381 101589 103432 101739 102794 129472 101305 101834 103124 101486 101254 102874 101481 | 103905

---

为什么您认为StringTokenizer是这样的？我认为您的character方法已经足够好了，如果您不同时在太多数据上运行它的话。（不过，我不确定在大量数据的情况下，正则表达式是否会更快）。请注意，循环和

StringTokenizer

方法的作用并不完全相同。

isSpace

方法已被弃用…@supersam654:

indexOf

不是as

StringTokenizer

，如果我们使用默认设置（空格、制表符等），那么它就不具有可扩展性。第二个选项将替换所有空白并创建一个句子，并将计算该句子中的所有字符长度。如果要计算字数，则您的

noSpaces

将以

“noSpaceString”

失败。我无法理解您试图用代码做什么。

int noChar=toExamine.length-noSpaces;

// Percentage of non-space over space is approximately 0.857 // Length of the full string generated is 1 075 662 0.857 1075662 // Name_of_method (Result): 15_Runs_In_Microseconds | Average_In_Microseconds countWords_1 (131489): 20465 20240 21045 20193 20000 19972 20551 39489 19859 19971 19889 19877 20049 19900 19949 | 21429 countWords_2 (131489): 255500 258723 254543 255956 253606 263549 254096 254402 254191 254296 253752 261501 260788 261574 254178 | 256710 countWords_3 (131489): 26225 25022 24830 24829 24545 24819 25459 24625 25628 24700 24936 24794 24794 24849 25026 | 25005 countWords_4 (131489): 24537 24169 25283 24862 23863 23902 24068 23906 51472 23731 23889 23844 23832 24275 23896 | 25968 countWords_5 (131489): 81087 112095 80008 81290 81472 80581 80717 80460 79870 80557 80694 80923 145686 80564 80849 | 87123 countWords_6 (131489): 114391 114146 111946 111873 112331 167207 134117 118217 112843 112804 113533 111834 112830 112392 118181 | 118576 countChars_1 (922546): 150507 109102 150453 111352 149753 108099 153842 109034 150817 117258 149219 108194 152839 110340 149524 | 132022 countChars_2 (922546): 28779 29473 52499 27182 26519 27743 26717 27161 26451 27060 26307 27309 26350 62824 33134 | 31700 countChars_3 (922546): 25408 25127 24980 24832 24624 24671 24848 24712 24634 24622 24607 24613 24661 24765 24883 | 24799 countChars_4 (922546): 81489 82246 80906 80718 80803 81147 81113 81798 81030 81024 108508 80768 80780 80671 80753 | 82916 countChars_5 (922546): 26086 25546 24846 43734 25016 25083 24894 25530 25031 25041 25114 24935 25358 24895 43498 | 27640 countChars_6 (922546): 102559 102257 101381 101589 103432 101739 102794 129472 101305 101834 103124 101486 101254 102874 101481 | 103905

import java.util.regex.Pattern;
import java.util.regex.Matcher;

import java.util.Arrays;
import java.util.ArrayList;
import java.util.Random;
import java.util.StringTokenizer;

import java.lang.reflect.Method;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.annotation.ElementType;

class TestStringProcessing_15028652 {

  @Retention(RetentionPolicy.RUNTIME)
  @Target(ElementType.METHOD)
  private @interface Test {};

  // From 0.80 - 0.90 (4:1 to 9:1 non-space:space characters ratio)
  private static final double NON_SPACE_RATIO = 0.85;
  private static final double NON_SPACE_RATIO_FLUCTUATION = 0.05;

  // With the way the test is written, it is not going to work well with small input (1000 is NOT enough)
  // Currently set to 700 000 - 1 300 000 characters
  private static final int NUM_CHARS = 1000000;
  private static final int NUM_CHARS_FLUCTUATION = 300000;

  // Some whitespace characters
  private static final char WHITESPACES[] = {' ', '\t', '\r', '\n'};

  // Number of times to run all methods
  private static final int NUM_OUTER = 5;
  // Number of times to run each method
  private static final int NUM_REPEAT = 15;

  static {
    for (int i = 0; i < WHITESPACES.length; i++) {
      assert(Character.isWhitespace(WHITESPACES[i]));
    }
  }

  private static Random random = new Random();

  private static String generateInput() {

    double nonSpaceRatio = NON_SPACE_RATIO + random.nextDouble() * 2 * NON_SPACE_RATIO_FLUCTUATION - NON_SPACE_RATIO_FLUCTUATION;
    int numChars = NUM_CHARS + random.nextInt(2 * NUM_CHARS_FLUCTUATION) - NUM_CHARS_FLUCTUATION;

    System.out.printf("%.3f %d\n", nonSpaceRatio, numChars);

    StringBuffer output = new StringBuffer();

    for (int i = 0; i < numChars; i++) {
      if (random.nextDouble() < nonSpaceRatio) {
        output.append((char) (random.nextInt(64) + '0'));
      } else {
        output.append(WHITESPACES[random.nextInt(WHITESPACES.length)]);
      }
    }

    return output.toString();
  }

  private static ArrayList<Method> getTestMethods() {
    Class<?> klass = null;
    try {
      klass = Class.forName(Thread.currentThread().getStackTrace()[1].getClassName());
    } catch (Exception e) {
      e.printStackTrace();
      System.err.println("Something really bad happened. Bailling out...");
      System.exit(1);
    }
    Method[] methods = klass.getMethods();
    // System.out.println(klass);
    // System.out.println(Arrays.toString(methods));

    ArrayList<Method> testMethods = new ArrayList<Method>();

    for (Method method: methods) {
        if (method.isAnnotationPresent(Test.class)) {
          testMethods.add(method);
        }
    }

    return testMethods;
  }


  public static void runTestReflection() {
    ArrayList<Method> methods = getTestMethods();

    for (int t = 0; t < NUM_OUTER; t++) {
      String input = generateInput();

      for (Method method: methods) {

        try {
          System.out.print(method.getName() + " (" + method.invoke(null, input) + "): ");
        } catch (Exception e) {
          e.printStackTrace();
        }

        long sum = 0;
        for (int i = 0; i < NUM_REPEAT; i++) {
          long start, end;
          Object result;

          try {
            start = System.nanoTime();
            result = method.invoke(null, input);
            end = System.nanoTime();

            System.out.print((end - start) / 1000 + " ");
            sum += (end - start) / 1000;
          } catch (Exception e) {
            e.printStackTrace();
          }
        }

        System.out.println("| " + sum / NUM_REPEAT);
      }

      System.out.println();
    }
  }

  public static void main(String args[]) {
    runTestReflection();
  }

  @Test
  public static int countWords_1(String input) {
    // WARNING: This is NOT the same as isWhitespace, since isWhitespace
    // also consider Unicode characters.
    return new StringTokenizer(input).countTokens();
  }

  @Test
  public static int countWords_2(String input) {
    return input.replaceAll("\\S+", "$0 ").length() - input.length();
  }

  @Test
  public static int countWords_3(String input) {
    int count = 0;
    boolean in = false;

    for (int i = 0; i < input.length(); i++) {
      if (!Character.isWhitespace(input.charAt(i))) {
        if (!in) {
          in = true;
          count++;
        }
      } else {
        in = false;
      }
    }

    return count;
  }

  @Test
  public static int countWords_4(String input) {
    int count = 0;

    for (int i = 0; i < input.length(); i++) {
      if (!Character.isWhitespace(input.charAt(i))) {
        do {
          i++;
        } while (i < input.length() && !Character.isWhitespace(input.charAt(i)));
        count++;
      }
    }

    return count;
  }

  @Test
  public static int countWords_5(String input) {
    int count = 0;
    Matcher m = p.matcher(input);

    while (m.find()) {
      count++;
    }

    return count;
  }

  @Test
  public static int countWords_6(String input) {
    return input.replaceAll("\\s*+\\S++\\s*+", " ").length();
  }

  @Test
  public static int countChars_1(String input) {
    return input.replaceAll("\\s+", "").length();
  }

  @Test
  public static int countChars_2(String input) {
    int count = 0;
    for (char c: input.toCharArray()) {
      if (!Character.isWhitespace(c)) {
        count++;
      }
    }

    return count;
  }

  @Test
  public static int countChars_3(String input) {
    int count = 0;
    for (int i = 0; i < input.length(); i++) {
      if (!Character.isWhitespace(input.charAt(i))) {
        count++;
      }
    }

    return count;
  }

  private static Pattern p = Pattern.compile("\\S+");

  @Test
  public static int countChars_4(String input) {
    Matcher m = p.matcher(input);
    int count = 0;

    while (m.find()) {
      count += m.end() - m.start();
    }

    return count;
  }

  @Test
  public static int countChars_5(String input) {
    int count = input.length();
    for (int i = 0; i < input.length(); i++) {
      if (Character.isWhitespace(input.charAt(i))) {
        count--;
      }
    }

    return count;
  }

  @Test
  public static int countChars_6(String input) {
    return input.length() - input.replaceAll("\\S+", "").length();
  }
}