我的“二分查找算法”实现

这是我的“二分查找算法”Java 实现！

/*
 * 练习：二分查找算法
 * 功能：查找一堆数据中是否存在某个要查找的数据
 * 作者：陈沛锐
 * 时间：2013.03.25
 * caution:this class import the package part01.charter02 for create a string sorted data
 */
package part01.chapter02;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class _2exercise {

    public static void main(String[] args) {
//        int[] A = { 1, 3, 5, 7, 9, 2, 4, 6, 8, 10 };
//        MERGE_SORT merge_sort = new MERGE_SORT();
//        merge_sort.sort(A, 0, 9);
        // create data
         System.out.println("Please inter a int number for datum counts:");
         Scanner scanner = new Scanner(System.in);
         int leng = scanner.nextInt();
         CreateDate createDate = new CreateDate(leng);
         int[] A = createDate.create();
         //sort data by MERGE_SORT()
         MERGE_SORT merge_sort = new MERGE_SORT();
         merge_sort.sort(A, 0, leng - 1);
        // output sorted data
        System.out.println("the sorted data are follow:");
        for (int i = 0; i < leng; i++) {
            System.out.print(A[i] + " ");
        }
        System.out.println();
        BinaryFind myBinaryFind = new BinaryFind();
        System.out.println("enter the number you want to find:");
        if (myBinaryFind.binaryFind(A, 0, A.length - 1, scanner.nextInt())) {
            System.out.println("existence!");
        } else {
            System.out.println("inexistence!");
        }
    }
}

class BinaryFind {
    public boolean binaryFind(int[] A, int p, int r, int s) {// 0,9,3;5,9,3;
        // flag sign existence or not
        boolean flag = false;
        if (A.length > 0 && p <= r) {
            int q = (p + r);// 2;7;
            if (A[q] == s) {// A[4]==5;8;
                flag = true;
                return flag;
            } else {
                if (A[q] < s) {
                    flag = binaryFind(A, q + 1, r, s);
                } else {
                    flag = binaryFind(A, p, q - 1, s);// 5,9;
                }
            }
        }
        return flag;
    }

    // find number and return it's first substance
    public int find_first(int[] A, int p, int r, int s) {
        int sub = 0;
        if (A.length > 0) {
            for (int i = p; i < r + 1; i++) {
                if (A[i] == s) {
                    sub = i;
                }
            }
        }
        return sub;
    }

    // find all same number and return all their substances
    public List<Integer> find_all(int[] A, int p, int r, int s) {
        // create a integer List<Integer> to store all same number's substances
        List<Integer> subList = new ArrayList<Integer>();
        if (A.length > 0) {
            for (int i = p; i < r; i++) {
                if (A[i] == s) {
                    subList.add(i);
                }
            }
        }
        return subList;
    }
}