Java基础之一组有用的类——使用二叉树搜索算法搜索某个作者（TryBinarySearch）

控制台程序。

Arrays类中的binarySearch()静态方法使用二叉树搜索算法，在有序数组中查找包含给定值的元素。只有当数组的元素按升序方式排序时，该方法才是最有效的，否则就应在调用binarySearch()方法之前调用sort()方法。

binarySearch()方法的所有版本都返回int类型的值，也就是在array中找到value的索引位置。当然，value也可能不在数组中，此时返回一个负整数。计算过程是：提取大于value的第一个元素的索引位置，翻转元素的取值符号后再减1.

public class Person implements Comparable<Person> {
  // Constructor
  public Person(String firstName, String surname) {
    this.firstName = firstName;
    this.surname = surname;
  }

  @Override
  public String toString() {
    return firstName + " " + surname;
  }

  // Compare Person objects
  public int compareTo(Person person) {
    int result = surname.compareTo(person.surname);
    return result == 0 ? firstName.compareTo(person.firstName) : result;
  }

  public String getFirstName() {
    return firstName;
  }

  public String getSurname() {
    return surname;
  }
  private String firstName;                                            // First name of person
  private String surname;                                              // Second name of person
}

import java.util.Arrays;

public class TryBinarySearch {
  public static void main(String[] args) {
    Person[] authors = {
            new Person("Danielle", "Steel"), new Person("John", "Grisham"),
            new Person("Tom", "Clancy"),     new Person("Christina", "Schwartz"),
            new Person("Patricia", "Cornwell"), new Person("Bill", "Bryson")
                       };


    Arrays.sort(authors);                                              // Sort using Comparable method

    System.out.println("
Order after sorting into ascending sequence:");
    for(Person author : authors) {
      System.out.println(author);
    }

    // Search for authors
    Person[] people = {
         new Person("Christina", "Schwartz"),    new Person("Ned", "Kelly"),
         new Person("Tom", "Clancy"),        new Person("Charles", "Dickens")
                      };
     int index = 0;
    System.out.println("
In search of authors:");
    for(Person person : people) {
      index = Arrays.binarySearch(authors, person);
      if(index >= 0) {
        System.out.println(person + " was found at index position " + index);
      } else {
        System.out.println(person + " was not found. Return value is " + index);
      }
    }
  }
}