如何在Java中以.i递增字符串？

Question

My goal is to add value pairs to a HashMap and if a value is already taken it will increment the previous value by .i. What I mean by this is it would start as 0.1 ... 0.9 then 0.10 , 0.11 , 0.12 and so on...

I have started:

for (int i=0; i < 50; i++){
    Double test = Double.parseDouble( 0 + "." + i);

But I cannot find a suitable test to add a decimal place onto the double once it has reached .9 (0.9, 0.10) Everything that I've tried doesn't work reliably. I was wondering if anyone could help.

Answer 1

You can use DecimalFormat to get two decimal digits. The ".00" in the parameter tells the formatter to use two decimal places while the "#" means to display the whole number as it is

DecimalFormat df = new DecimalFormat("#.00");
    for(int i=0;i < 50 ;i++){
        Double test = Double.parseDouble( 0 + "." + i);
        System.out.println(df.format(test));

Output:

.00
.10
.20
.30
.40
.50
.60
.70
.80
.90
.10
.11
.12
.13
.14
.15
.16
.17
.18
.19
.20

Answer 2

What I mean by this is it would start as 0.1...0.9 then 0.10, 0.11,0.12 and so on...

To print this pattern, there simplest solution is to print the value as it really a String operation rather than a mathematical one.

for (int i = 1; i <= 50; i++) 
    System.out.println("0." + i);

NOTE: For double the value 0.1 == 0.10 and there is no way to tell them apart.

Answer 3

How about this

double division = 1.0;
for(int i=0;i < 50 ;i++){
    if (i%10 == 0)
        division *= 10;

    Double test = i/division;
    System.out.print(test + " ");
}

It will have duplicate each time it goes down one decimal, but I hope for testing it should be ok.