public int hashcode(String name) {		// generate unique number for each  book 
		int hash=500;
		name=name.toLowerCase();
		int len=name.length();
		int cnt=name.indexOf("java");
		int c0=name.indexOf("a");
		if(cnt>=0){
//			System.out.println("book contain java "+cnt);
			hash-=cnt;
			hash=hash-len-c0;
		}else{
			cnt=name.indexOf("php");
			if(cnt>=0){
//				System.out.println("book contain php "+cnt);
				hash+=cnt;
				hash=hash+len+c0;
			}else{
//				System.out.println("book contain other "+cnt);
				hash+=500;
			}
		}
		return hash;
	}