使用DecimalFormat方法

Question

1. Display y to three decimal places
2. Display how many digits come before the decimal point and how many comes after a number. On x , y and z
3. Create a string E that consists of D in reverse concatenated with F , including a space between them
4. Search for the substring 'i' in c and replace it for 'fff'

x = 123.456, y = 54/5, z = √2, D = “Decimal”, F = “Function”

I did this for question 1 and it works but I am not sure if this is how I am suppose to do this and I have not clue how to go about doing question 2,3 and 4. Any help would be appreciated.

double y = 54.0/5.0;
DecimalFormat y_format = new DecimalFormat("#.###"); 
String formatted_string1 = y_format.format(y);
System.out.println(formatted_string1);

Answer 1

For 2, you can divide the number by 10 until it reaches 0. A simple counter with a while loop would work well. You could so similar for the other case. (using multiplication)

For 3, Simply use a loop to read a character at a time from D and concatenate to a new String.

for ( i from D.length to 0)
  newString += D.charAt(i)
newString += F

For 4, check the replace method in String.