java实现二分查找法

package com.wj;

public class BinarySearch {

    public static void main(String[] args) {
        int len = 10000;
        int[] a = new int[len];
        for (int i = 0; i < len; ++i) {
            a[i] = i;
        }
        
        System.out.println(find(a, 56780));
        System.out.println(find(a, 5678));
        System.out.println(find2(a, 56780, 0, len - 1));
        System.out.println(find2(a, 5678, 0, len - 1));
    }

    private static int find(final int[] a, final int value) {
        int l = 0;
        int r = a.length - 1;
        
        while ( l <= r) {
            int mid = l + (r - l) / 2;
            
            if (a[mid] == value) {
                return mid;
            } else if (a[mid] < value) {
                l = mid + 1;
            } else {
                r = mid - 1;
            }
            
        }
        return -1;
    }
    
    
    private static int find2(final int[] a, final int value, final int l, final int r) {
        if (l > r) return -1;
        
        int mid = l + (r - l) / 2;
        
        if (a[mid] == value) {
            return mid;
        } else if (a[mid] < value) {
            return find2(a, value, mid + 1, r);
        } else {
            return find2(a, value, l, mid - 1);
        }
    }
}