测试十进制转换为二进制

	public static String ToBinaryString(int scanStr){
		final String FINAL_ONESTRING = "11111111111111111111111111111111";
		final String FINAL_MIN_VALUE = "10000000000000000000000000000000";
		switch (scanStr) {
		case 0 : return "0"; 
		case 1 : return "1"; 
		case -1 : return FINAL_ONESTRING;
		case Integer.MIN_VALUE : return FINAL_MIN_VALUE; 
		}
		boolean fushuFlag = scanStr < 0;
		if (fushuFlag)
			scanStr = 0 - scanStr;
		StringBuilder sb = new StringBuilder();//默认16字符
		while (scanStr != 1){
			int yushu = scanStr % 2;
			scanStr = scanStr >> 1;
     		sb = sb.append(yushu);
     	}
		sb = sb.append(1);//补首位
		if (fushuFlag){
			int sblength = sb.length();
			for(int i = 0; i< sblength;i++){//对正数进行取反操作
				char charAt = sb.charAt(i);
				if(charAt == '1')
					sb.setCharAt(i, '0');
				else
					sb.setCharAt(i, '1');
			}
			if(sb.charAt(0) == '1'){//首位是1 进行加法计算
				int index = sb.indexOf("0",1);//一个值为0的offset
				sb.setCharAt(index, '1');//进位计算
				for(int i = 0; i < index; i++)
					sb.setCharAt(i, '0');//index前面的值全部置0
			}else{
				sb.setCharAt(0, '1');
			}
			return FINAL_ONESTRING.substring(sb.length()) + sb.reverse().toString();	
		}
		return sb.reverse().toString();	
}//

 

		long flag1 = System.currentTimeMillis();
		for(int i = 0; i<10000000; i++){
			Integer.toBinaryString(154);
		}
		long flag2 = System.currentTimeMillis();
		
		for(int i = 0; i<10000000; i++){
			ToBinaryString(154);
		}
		long flag3 = System.currentTimeMillis();
		
		System.out.println(flag2 - flag1);//测试input:154 执行1000W次 耗时 15672
		System.out.println(flag3 - flag2);//测试input:154 执行1000W次 耗时 37781