如何在数组中添加前缀 0？

Question

I am writing a Java program that trims an array of numbers to length 10. If the array is shorter than 10, then the program should prefix the array with 0s until it is length 10.

Example:

 1234567890 :: 1234567890 12345678990:: 1234567899 1234 :: 0000001234

    int[] aa= new int[]{123456789};
    if(aa.length==10)
    {
        for (int i=0;i<=aa.length;i++)
        {
             system.out.println(aa[i]);
        } 
    }
    if(aa.length>0)
    {
        for(int i=0;i<=10;i++)
        {
            system.out.println(aa[i]);
        }
    }
    if(aa.length<10)
    {
        for(int i=0;i<=10;i++)
        {
            system.out.println(aa[i]);
        }
    }

Is there something wrong in my code?

Answer 1

First of all, arrays of dynamic size makes me think you want to do an ArrayList, not an array. Still, if for some reason you are dealing with actual arrays of different length, it will be something like this.

import java.util.Arrays;

public class Test {
    public static void main(String[] args) {
        int[] lessThanTen = new int[] {1,2,3,4};
        int[] newArr = new int[10];

        int numZeros = 10 - lessThanTen.length;

        for (int i = 0; i < 10; i++) {
            if (i < numZeros) {newArr[i] = 0;}
            else {newArr[i] = lessThanTen[i - numZeros];}
        }

        System.out.println(Arrays.toString(newArr));
    }
}

Answer 2

First, an int can't have more than 10 digits so I am going to presume you are using longs .

1. To determine the number of digits in any integral number, use Math.log10() .
2. If the number has <= 10 digits, use the printf specifier of %010d which allows for a field of 10 digits, padded on the left with 0's.
3. Otherwise, convert to a string and print the first 10 digits using String.substring();

      for (long n : new long[] { 123,12,1, 1234579911111L, 1234567890
      }) {
         if (Math.log10(n) <= 10) {
            System.out.printf("%010d%n", n);
         }
         else {
            System.out.printf("%s%n", Long.toString(n).substring(0, 10));
         }
      }

The above prints the following:

0000000123
0000000012
0000000001
1234579911
1234567890

If you are reading in the values as strings, then you can just do the following.

1. If the string is greater >= 10 characters, take the substring of the first 10.
2. If the string is less < 10, then pad on the left with zeroes, as required.

      for (String s : new String[] {
            "123", "12", "1", "1234579911111", "1234567890"
      }) {
         int len = s.length();
         String n = len >= 10 ? s.substring(0, 10)
               : "0000000000".substring(len, 10) + s;
         System.out.println(n);
      }

The above prints the following:

0000000123
0000000012
0000000001
1234579911
1234567890

Answer 3

An integer cannot have 10 digits, use a long instead. Also, use string to solve the problem rather than arrays.

public static void main(String[] args) {
    Scanner cmdScanner = new Scanner(System.in);
    System.out.println("Enter a number");
    long num = cmdScanner.nextLong();
    String input = String.valueOf(num);
    if (input.length() > 10) {
        System.out.println(input.substring(0, 10));
    } else {
        final int zerosToAppend = 10 - input.length();
        final StringBuilder sb = new StringBuilder();
        for (int i = 0; i < zerosToAppend; i++) {
            sb.append("0");
        }
        System.out.println(sb.append(input));
    }
    cmdScanner.close();
}

Answer 4

You can do by simply writing this program:-

import java.util.Arrays;
public class Test
{
    public static void main(String[] args)
    {
        int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        int newarray[] = new int[10];
        //If it is smaller than 10
        if(arr.length<10)
        {
            for(int i=0;i<(10-arr.length);i++)
            {                       
                newarray[i] = 0;
            }
            for(int i=(10-arr.length);i<10;i++)
            {
                newarray[i] = arr[i-(10-arr.length)];
            }
        }
        else
        {
            for(int i=0;i<arr.length;i++)
            {               
                newarray[i] = arr[i];
            }
        }
        System.out.println(Arrays.toString(newarray));
    }
}

Hope this will Help