System.out.println("输入一个十进制数:");
Scanner sc = new Scanner(System.in);
int num = sc.nextInt();
String str = "";
//转化
for(;num != 0;){
int i = num % 2;
//颠倒前后位置
str = i + str;
num = num / 2;
}
System.out.println(str);