Java程序通过使用二分搜索比较器从列表中搜索用户定义的对象

public static int binarySearch(primitive() p,Primitive key)
public static int binarySearch(Object() o,Object key)

public static int binarySearch(Object() o,Object key,Comparator c)
Java Collections binarySearch(List<? extends Comparable1<? super R>> list, R key)and;
Java Collections binarySearch(List<? extends R> list, R key, Comparator<? super R> c)

import java.util.*;

public class Binarysearch {
   public static void main(String[] args){
      List<Domain> l1 = new ArrayList<Domain>();
      l1.add(new Domain(100, "India"));
      l1.add(new Domain(200, "Bangladesh"));
      l1.add(new Domain(300, "Dhaka"));
      l1.add(new Domain(400, "Kolkata"));

      Comparator<Domain> c = new Comparator<Domain>() {
      	 public int compare(Domain u1, Domain u2) {
            return u1.getId().compareTo(u2.getId());
      	 }
      };
      int index = Collections.binarySearch(	l1, new Domain(10, null), c);
      System.out.println("Found at index number zone" + index);
      index = Collections.binarySearch(l1, new Domain(6, null), c);
      System.out.println(index);
   }
}
class Domain {
   private int id;
   private String url;
   public Domain(int id, String url){
      this.id = id;
      this.url = url;
   }
   public Integer getId() { return Integer.valueOf(id); }
}

Found at index number zone-1
-1

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class ascendingsearch {
	public static void main(String[] args){
      List<Integer> ak = new ArrayList<integer>();
      ak.add(100);
      ak.add(200);
      ak.add(30);
      ak.add(10);
      ak.add(20);

      int index = Collections.binarySearch(ak, 100);
      System.out.println(index);
      index = Collections.binarySearch(ak, 130);
      System.out.println(index);
	}
}
</integer>

Note: ascendingsearch.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
-6
-6

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class binsearchdecend {
	public static void main(String[] args){
      List<Integer> a0710 = new ArrayList<Integer>();
      a0710.add(1000);
      a0710.add(500);
      a0710.add(300);
      a0710.add(10);
      a0710.add(2);
      int index = Collections.binarySearch(
      	a0710, 50, Collections.reverseOrder());

      System.out.println("Found at index number present " + index);
	}
}

Found at index number present -4

import java.util.Scanner;
public class BinarySearchExample{
   public static void main(String args[]){
      int counter, num, item, array[], first, last, middle;
      Scanner input = new Scanner(System.in);
      System.out.println("Enter number of elements:");
      num = input.nextInt(); 
      array = new int[num];

      System.out.println("Enter " + num + " integers");
      for (counter = 0; counter < num; counter++)
          array[counter] = input.nextInt();

      System.out.println("Enter the search value:");
      item = input.nextInt();
      first = 0;
      last = num - 1;
      middle = (first + last)/2;

      while( first <= last ){
         if ( array[middle] < item )
           first = middle + 1;
         else if ( array[middle] == item ){
           System.out.println(item + " found at location " + (middle + 1) + ".");
           break;
         }
         else{
             last = middle - 1;
         }
         middle = (first + last)/2;
      }
      if ( first > last )
         System.out.println(item + " is not found.\n");
   }
}

Enter number of elements:
7
Enter 7 integers
10
12
56
42
48
99
100
Enter the search value:
50
50 is not found.