Android Java检查字符串长度 - 30的倍数

Question

My situation: I have a string (called str). The length of the string must be a multiple of 30 (eg 30, 60, 90). If the length of the str is not a multiple of 30, add spaces " " to the end of it.

Something like this:

if (str.length() / 30 != ????) {
//add spaces to the end
}

Of course, the code above is not correct. It would be very appreciated if you could help me with this.

Thanks in advance!

Answer 1

this code is not tested but i guess it will work:

int a = str.length()%30;

for(int i=0; i<=a; i++)
str = str + " ";

Answer 2

You can quite simply do:

if(str.length()%30!=0)
        str = String.format("%1$-"+(((str.length()/30)*30)+30)+"s", str);  

• str.length()%30 gives the remainder on dividing the length by 30. If it is not 0, then you have to add spaces.

• String.format("%1$-"+(((str.length()/30)*30)+30)+"s", str) adds the spaces to the right of the String.

---

Or even simply, you can do:

while(str.length()%30 !=0)
    str+= ' ';

Answer 3

What would you do to check if a number is a multiple of 30 in simple Maths ?

Yes, you would divide and check if the remainder is 0 or not, right?

That's how you'll do it in Java . To get the remainder in Java , Modulus(%) operator is used. So, you can do it like this :

if (str.length() % 30 != 0) {
    //add spaces to the end
    str += " ";
}

or if you want to add spaces to make the length a multiple of 30, then do this:

int remainder = str.length() % 30;
if (remainder != 0) {
    //add spaces to the end
    int numSpacesRequired = 30-remainder; //no. of spaces reuired to make the length a multiple of 30
    for(int i = 0; i < numSpacesRequired; i++)
        str += " ";
}

Read more about the basic operators in Java here .

Answer 4

You can use Modulo to achieve that:

if (str.length() % 30 != 0) {
     //add spaces to the end
     str += ' ';
}

Answer 5

Simply: (Tested and worked)

public static void main(String[] args) {
    String str = "AYOA"; //Length is only 4

    //If the remainder of the str's length is not 0 (Not a multiple) 
    if (str.length() % 30 != 0){ 
        str += ' ';
    }

    System.out.println("[" + str + "]"); //A space is added at the back
}

If you want to add the space continuously until the length is a multiple of 30:

 public static void main(String[] args) {
    String str = "AYOA"; //Length is only 4

    //If the remainder of the str's length is not 0 (Not a multiple)
    //Repeat until is multiple of 30
   while(str.length % 30 != 0){
        str += ' ';
    }

    System.out.println("[" + str + "]"); //A space is added at the back
}

Answer 6

use StringBuilder to build whitespaces

    String str="multiple of 30";
    int spacesNum=str.length()%30; //get the remainder
    StringBuilder spaces=new StringBuilder(); //build white spaces
    for(int j=0;j<spacesNum;j++){
        spaces.append(' ');
    }
    System.out.println(str+spaces.toString());