二分查找

package sort;

public class BinarySearch {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        
        int[] a={70,80,31,37,10,1,48,60,33,80};
            
        QuickSort.quickSort(a);
        
        System.out.println(binarySearch(a,31));
    }
    
    private static int binarySearch(int[] a, int element) {
        // TODO Auto-generated method stub
        
        int low,min,upper;
        
        low=0;
        upper=a.length-1;
        
        while(low<=upper){
            min=(low+upper)/2;
            
            if(a[min]>element)
                upper=min-1;
            else if(a[min]<element)
                low=min+1;
            else
                return min;
        }
        
        return -1;
    }
}