Message format in java and how to replicate the same in Golang

Question

Here's the Java code:

AtomicInteger obIndex = new AtomicInteger(0);
MessageFormat.format("{0,number,#},{1},{2},{3},\"{4}\"",
    obIndex.getAndIncrement(),
    "5bb2b35c67525f9e845648df370652b8",
    "Vm:vm-289",
    "1.1.1.1:113",
    "ABC-Testvm-1");

Output:

0,5bb2b35c67525f9e845648df370652b8,Vm:vm-289,1.1.1.1:113,"ABC-Testvm-1"

I tried this in Go:

value := fmt.Sprintf("%d,%s,%s,%s,%s",
    0,
    "5bb2b35c67525f9e845648df370652b8",
    "Vm:vm-289",
    "1.1.1.1:113", "ABC-Testvm-1")
fmt.Println(value)

Which outputs:

0,5bb2b35c67525f9e845648df370652b8,Vm:vm-289,1.1.1.1:113,ABC-Testvm-1

What is the significance of {0,number,#} and how can I get the same in Go?

Answer 1

This is detailed at java.text.MessageFormat . The string you pass to MessageFormat.format() is a pattern . A pattern consists of format elements . The form of a format element is:

 FormatElement:
         { ArgumentIndex }
         { ArgumentIndex , FormatType }
         { ArgumentIndex , FormatType , FormatStyle }

So in the first format element:

{0,number,#}

0 is the argument index whose value to format.

number is a format type, and # is a format style, more specifically a subformat pattern . This means the argument will be formatted using a subformat of:

new DecimalFormat(subformatPattern, DecimalFormatSymbols.getInstance(getLocale()))

The # subformat is described at java.text.DecimalFormat . It simply means to not use fraction digits, only display it as an integer, and if it is not an integer, it will be rounded (using the RoundingMode.HALF_EVEN mode).

In Go to format an integer number, you may simply use the %d verb as you did, which will yield the same output format for integer numbers. If the number is a floating point number, this won't work ( %d can only be used for integers). If the number is a floating point number, use the %f verb, more specifically %.0f to tell it to round to an integer, or the shortest form %.f .

Also your Java version puts the last argument in double quotes, so you should do the same in Go.

value := fmt.Sprintf("%d,%s,%s,%s,\"%s\"",
    0,
    "5bb2b35c67525f9e845648df370652b8",
    "Vm:vm-289",
    "1.1.1.1:113", "ABC-Testvm-1")

fmt.Println(value)

This will output (try it on the Go Playground ):

0,5bb2b35c67525f9e845648df370652b8,Vm:vm-289,1.1.1.1:113,"ABC-Testvm-1"