testsetperformance.java

JAVA 经典代码

import java.util.*;

public class  TestSetPerformance {
  private static int REPTEXEC = 10000;
  private static int QUANTITY = 100;

  public static void main(String[] args) {
    System.out.println(REPTEXEC + " repetitions");
    testSet(new TreeSet());
    testSet(new HashSet());
    testSet(new LinkedHashSet());
  } // main方法结束

  public static void fill(Collection c, int count) {
    for(int i = 0; i < count; i++)
      c.add(Integer.toString(i));
  } // fill方法结束

  public static void testSet(Set a) {
    System.out.println("_____________________________________");
    System.out.println("测试" + a.getClass().getName().replaceAll("\\w+\\.", ""));

    fill(a, QUANTITY);

    // 测试size()
    long start = System.currentTimeMillis();
    for (int i = 0; i < REPTEXEC; i++) {
      for (int j = 0; j < QUANTITY; j++)
        a.size();
    }
    long end = System.currentTimeMillis();
    System.out.println("取大小操作用时: " + (end - start));

    // 测试迭代操作
    start = System.currentTimeMillis();
    for (int i = 0; i < REPTEXEC; i++) {
      Iterator it = a.iterator();
      while (it.hasNext())
        it.next();
    }
    end = System.currentTimeMillis();
    System.out.println("迭代操作用时: " + (end - start));

    // 测试包含操作
    for(int i = 0; i < REPTEXEC; i++)
    a.contains(Integer.toString(i));
    end = System.currentTimeMillis();
    System.out.println("包含操作用时: " + (end - start));

    // 测试增加操作
    String s = "test";
    start = System.currentTimeMillis();
    for (int j = 0; j < REPTEXEC * 10; j++)
      a.add(s);
    end = System.currentTimeMillis();
    System.out.println("增加操作用时: " + (end - start));
  } // testSet方法结束
} // TestSetPerformance方法结束