How to format a number 0..9 to display with 2 digits (it's NOT a date)
You can use:
String.format("%02d", myNumber)
See also the javadocs
Is it possible to have placeholders in strings.xml for runtime values?
Formatting and Styling
Yes, see the following from String Resources: Formatting and Styling
If you need to format your strings using
String.format(String, Object...)
, then you can do so by putting your format arguments in the string resource. For example, with the following resource:<string name="welcome_messages">Hello, %1$s! You have %2$d new messages.</string>
In this example, the format string has two arguments:
%1$s
is a string and%2$d
is a decimal number. You can format the string with arguments from your application like this:Resources res = getResources();
String text = String.format(res.getString(R.string.welcome_messages), username, mailCount);
Basic Usage
Note that getString
has an overload that uses the string as a format string:
String text = res.getString(R.string.welcome_messages, username, mailCount);
Plurals
If you need to handle plurals, use this:
<plurals name="welcome_messages">
<item quantity="one">Hello, %1$s! You have a new message.</item>
<item quantity="other">Hello, %1$s! You have %2$d new messages.</item>
</plurals>
The first mailCount
param is used to decide which format to use (single or plural), the other params are your substitutions:
Resources res = getResources();
String text = res.getQuantityString(R.plurals.welcome_messages, mailCount, username, mailCount);
See String Resources: Plurals for more details.
How to Automatically add thousand separators as number is input in EditText
You can use String.format()
in a TextWatcher
. The comma in the format specifier does the trick.
This does not work for floating point input. And be careful not to set an infinite loop with the TextWatcher.
public void afterTextChanged(Editable view) {
String s = null;
try {
// The comma in the format specifier does the trick
s = String.format("%,d", Long.parseLong(view.toString()));
} catch (NumberFormatException e) {
}
// Set s back to the view after temporarily removing the text change listener
}
How do I print a double value without scientific notation using Java?
You could use printf()
with %f
:
double dexp = 12345678;
System.out.printf("dexp: %f\n", dexp);
This will print dexp: 12345678.000000
. If you don't want the fractional part, use
System.out.printf("dexp: %.0f\n", dexp);
0 in %.0f
means 0 places in fractional part i.e no fractional part. If you want to print fractional part with desired number of decimal places then instead of 0 just provide the number like this %.8f
. By default fractional part is printed up to 6 decimal places.
This uses the format specifier language explained in the documentation.
The default toString()
format used in your original code is spelled out here.
How to go about formatting 1200 to 1.2k in java
Here is a solution that works for any long value and that I find quite readable (the core logic is done in the bottom three lines of the format
method).
It leverages TreeMap
to find the appropriate suffix. It is surprisingly more efficient than a previous solution I wrote that was using arrays and was more difficult to read.
private static final NavigableMap<Long, String> suffixes = new TreeMap<> ();
static {
suffixes.put(1_000L, "k");
suffixes.put(1_000_000L, "M");
suffixes.put(1_000_000_000L, "G");
suffixes.put(1_000_000_000_000L, "T");
suffixes.put(1_000_000_000_000_000L, "P");
suffixes.put(1_000_000_000_000_000_000L, "E");
}
public static String format(long value) {
//Long.MIN_VALUE == -Long.MIN_VALUE so we need an adjustment here
if (value == Long.MIN_VALUE) return format(Long.MIN_VALUE + 1);
if (value < 0) return "-" + format(-value);
if (value < 1000) return Long.toString(value); //deal with easy case
Entry<Long, String> e = suffixes.floorEntry(value);
Long divideBy = e.getKey();
String suffix = e.getValue();
long truncated = value / (divideBy / 10); //the number part of the output times 10
boolean hasDecimal = truncated < 100 && (truncated / 10d) != (truncated / 10);
return hasDecimal ? (truncated / 10d) + suffix : (truncated / 10) + suffix;
}
Test code
public static void main(String args[]) {
long[] numbers = {0, 5, 999, 1_000, -5_821, 10_500, -101_800, 2_000_000, -7_800_000, 92_150_000, 123_200_000, 9_999_999, 999_999_999_999_999_999L, 1_230_000_000_000_000L, Long.MIN_VALUE, Long.MAX_VALUE};
String[] expected = {"0", "5", "999", "1k", "-5.8k", "10k", "-101k", "2M", "-7.8M", "92M", "123M", "9.9M", "999P", "1.2P", "-9.2E", "9.2E"};
for (int i = 0; i < numbers.length; i++) {
long n = numbers[i];
String formatted = format(n);
System.out.println(n + " => " + formatted);
if (!formatted.equals(expected[i])) throw new AssertionError("Expected: " + expected[i] + " but found: " + formatted);
}
}
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