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Android String format not working

I have a problem with String.format In android I want replace { 0 } with my id.
My this code not working:
String str = "abc&id={0}";
String result = String.format(str, "myId");

I think you should use replace method instead of format.
String str = "abc&id={0}";
str.replace("{0}","myId");

you have 2 ways to do that and you are mixing them :)
1.String format:
String str = "abc&id=%s";//note the format string appender %s
String result = String.format(str, "myId");
or
2.Message Format:
String str = "abc&id={0}"; // note the index here, in this case 0
String result = MessageFormat.format(str, "myId");

You have to set your integer value as a seperate variable.
String str = "abc&id";
int myId = 001;
String result = str+myId;

try this,
String result = String.format("abc&id=%s", "myId");
edit if you want more than one id,
String.format("abc&id=%s.id2=%s", "myId1", "myId2");

The syntax you're looking for is:
String str = "abc&id=%1$d";
String result = String.format(str, id);
$d because it's a decimal.
Other use case:
String.format("More %2$s for %1$s", "Steven", "coffee");
// ==> "More coffee for Steven"
which allows you to repeat an argument any number of times, at any position.

regex to match and replace two characters between string

I have a string String a = "(3e4+2e2)sin(30)"; and i want to show it as a = "(3e4+2e2)*sin(30)";
I am not able to write a regular expression for this.

Try this replaceAll:
a = a.replaceAll("\) *(\\w+)", ")*$1");

You can go with this
String func = "sin";// or any function you want like cos.
String a = "(3e4+2e2)sin(30)";
a = a.replaceAll("[)]" + func, ")*siz");
System.out.println(a);

this should work
a = a.replaceAll("\\)(\\s)*([^*+/-])", ") * $2");

String input = "(3e4+2e2)sin(30)".replaceAll("(\\(.+?\\))(.+)", "$1*$2"); //(3e4+2e2)*sin(30)

Assuming the characters within the first parenthesis will always be in similar pattern, you can split this string into two at the position where you would like to insert the character and then form the final string by appending the first half of the string, new character and second half of the string.
string a = "(3e4+2e2)sin(30)";
string[] splitArray1 = Regex.Split(a, #"^\(\w+[+]\w+\)");
string[] splitArray2 = Regex.Split(a, #"\w+\([0-9]+\)$");
string updatedInput = splitArray2[0] + "*" + splitArray1[1];
Console.WriteLine("Input = {0} Output = {1}", a, updatedInput);

I did not try but the following should work
String a = "(3e4+2e2)sin(30)";
a = a.replaceAll("[)](\\w+)", ")*$1");
System.out.println(a);

remove all characters between slashes in a URL in java

I have a url for examle:
http://www.abc.com/ABC/ABC-Boots-in-Leather/Prod/product.aspx?iid=34487
i have to convert it into:
http://www.abc.com/product.aspx?iid=34487
I am using a regex expression as :
String u = url.replaceAll("/.*?/","");
But it doesn't remove the text but just removes the slashes.? How should i correct it?

int x = url.indexOf('/');
int y = url.lastIndexOf('/')+1;
String u = url.substring(0, x) + url.substring(y);

String s = "http:www.abc.com/ABC/ABC-Boots-in-Leather/Prod/product.aspx?iid=34487";
String s1 = s.replaceAll("(/(.)*/)","/");
output: http:www.abc.com/product.aspx?iid=34487

Updated to changed question
Probably not simplest solution, but works
String url = "http://www.abc.com/ABC/ABC-Boots-in-Leather/Prod/product.aspx?iid=34487";
String u = "http:/" + url.replaceAll("(http://)|/.*/", "/");
Result:
http://www.abc.com/product.aspx?iid=34487

Deleting everything except last part of a String?

What kind of method would I use to make this:
http://www.site.net/files/file1.zip
To
file1.zip?

String yourString = "http://www.site.net/files/file1.zip";
int index = yourString.lastIndexOf('/');
String targetString = yourString.substring(index + 1);
System.out.println(targetString);// file1.zip

String str = "http://www.site.net/files/file1.zip";
str = str.substring(str.lastIndexOf("/")+1);

You could use regex to extract the last part:
#Test
public void extractFileNameFromUrl() {
final Matcher matcher = Pattern.compile("[\\w+.]*$").matcher("http://www.site.net/files/file1.zip");
Assert.assertEquals("file1.zip", matcher.find() ? matcher.group(0) : null);
}
It'll return only "file1.zip". Included here as a test as I used it to validate the code.

Use split:
String[] arr = "http://www.site.net/files/file1.zip".split("/");
Then:
String lastPart = arr[arr.length-1];
Update: Another simpler way to get this:
File file = new File("http://www.site.net/files/file1.zip");
System.out.printf("Path: [%s]%n", file.getName()); // file1.zip

Parse string starting from the end

I want to split string around only the last _ character , example:some_string_foo_bar into two substrings some_string_foo bar.
I tried to use Pattern and StringTokenizer, but they always start from the beginning of stirng. Any idea how to do this?

Use lastIndexOf; there's no reason to do a full split.

Sure, this might be of some use. Here's an example.
String source = "hello_world_foo";
int pos = source.lastIndexOf('_');
String before = source.substring(0, pos);
String after = source.substring(pos + 1);

You can use:
String strX = "some_string_foo";
String str1 = strX.substring(0,strX.lastIndexOf("_"));
String str2 = strX.subscting(strX.lastIndexOf("_"),strX.length());

String[] arr = str.split("_");
String lastOne = arr[arr.length-1];