Develop Reference

Replace parts of a string in Java

I need to replace parts of a string by looking up the System properties.
For example, consider the string It was {var1} beauty killed {var2}
I need to parse the string, and replace all the words contained within the parenthesis by looking up their value in System properties. If System.getProperty() returns null, then simply replace with empty character. This is pretty straightforward when I know the variables well ahead. But the string that I need to parse is not defined ahead. I wouldn't know how many number of variables are in the string and what the variable names are. Assuming a simple, well formatted string (no nested parenthesis, open - close matches), what is the simplest or the most elegant way to parse through the string and replace all the character sequences that are enclosed in the parenthesis?
Only solution I could come up with is to traverse the string from the first character, note down the positions of the start and end positions of the parenthesis, replace the string between them, and then continue until reaching the end of the string. Is there simpler way to do this?

You can use the parentheses to break the initial string into substrings, and then replace every other substring.
String[] substituteValues = {"the", "str", "other", "another"};
int substituteValuesIndex = 0;
String test = "Here is {var1} string called {var2}";
// split the string up into substrings
test = test.replaceAll("\\}", "\\{");
String[] splitString = test.split("\\{");
// now sub in your values
for (int k=1; k < splitString.length; k = k+2) {
splitString[k] = substituteValues[substituteValuesIndex];
substituteValuesIndex++;
}
String result = "";
for (String s : splitString) {
result = result + s;
}

Java: single line substring

I need to sub string the string after "2:" to the end of line as it is a changeable string:
Which mean in this example that I want to take the string "LOV_TYPE" from this 2 lines
ObjMgrSqlLog Detail 4 2014-03-26 13:19:58 Bind variable 2: LOV_TYPE
ObjMgrSqlLog Detail 4 2014-03-26 13:19:58 Bind variable 3: AUDIT_LEVEL
I tried to use subString(int startingIndex, int endingIndex) method, I can determine the first argument which is starting point.. but I can't determine the end point.

You can use two substrings, one that gets the String after 2:, and then one that gets the string before the next new line.
string = string.substring(string.indexOf("2:") + 2);
string = string.substring(0, string.indexOf("ObjMgrSqlLog));
If you need to get rid of the spaces on either end, you can then trim the string.
string = string.trim();

source:
String str = "ObjMgrSqlLog Detail 4 2014-03-26 13:19:58 Bind variable 2: LOV_TYPE";
You can use regex
String out1 = str.replaceAll("^.*?.\\:.*[ ]", "");
or classic index-of
int lastCh = str.lastIndexOf(":");
String out2 = str.substring(++lastCh).trim();
output:
System.out.println(out1);
System.out.println(out2);

If you use str.substring(startingIndex), you will have the substring to the end of the string. It seems to be what you want. If you have extra spaces at the end of the string, you can always use a str.trim() to remove the spaces.

Use substring along with .length() to get the value of the length of the string. For example:
String original = "ObjMgrSqlLog Detail 4 2014-03-26 13:19:58 Bind variable 2: LOV_TYPE";
String newString = original.substring (62, original.length ());
System.out.print (newString);

why does this for loop wordcount method not work in java

Can anyone let me know why this wordsearch method doesn't work - the returned value of count is 0 everytime I run it.
public int wordcount(){
String spaceString = " ";
int count = 0;
for(int i = 0; i < this.getString().length(); i++){
if (this.getString().substring(i).equals(spaceString)){
count++;
}
}
return count;
}
The value of getString = my search string.
Much appreciated if anyone can help - I'm sure I'm prob doing something dumb.
Dylan

Read the docs:
The substring begins with the character at the specified index and extends to the end of this string.
Your if condition is only true once, if the last character of the string is a space. Perhaps you wanted charAt? (And even this won't properly handle double spaces; splitting on whitespace might be a better option.)

Because substring with only one argument returns the sub string starting from that index till the end of the string. So you're not comparing just one character.
Instead of substring define spaceString as a char, and use charAt(i)

this.getString().substring(i) -> this returns a sub string from the index i to the end of the String
So for example if your string was Test the above would return Test, est, st and finally t
For what you're trying to do there are alternative methods, but you could simple replace
this.getString().substring(i)
with
spaceString.equals(this.getString().charAt(i))
An alternative way of doing what you're trying to do is:
this.getString().split(spaceString)
This would return an array of Strings - the original string broken up by spaces.

Read the documentation of the method you are using:
http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#substring(int)
I.e. the count will be non zero only if you have a space on the end of your string

Using substring as you are will not work. If the value of getString() is "my search string" every iteration through the loop with have substring(i) return:
my search string
y search string
search string
search string
earch string
arch string
rch string
ch string
h string
string
string
tring
ring
ing
ng
g
Notice none of those equals " ".
Try using split.
public int countWords(String s){
return s.split("\\s+").length;
}

Change
if (this.getString().substring(i).equals(spaceString))
to
if (this.getString().charAt(i) == ' ')

this.getString().substring(i) returns a string from the index of (i) to the end of the string.
Example: for i=5, it will return "rown cow" from the string "the brown cow". This functionality isn't what you need.
If you pepper System.out.println() throughout your code (or use the debugger), you will see this.
I think it would be better to use something like String.split() or charAt(i).
By the way, even if you fix your code by counting spaces, it will not return the correct value for these conditions: "my dog" (word count=2) and "cow" (word count=1). There is also a problem if there are more than one space between words. ALso, this will produce a word cound of three:
" the cow ".

Characters Being Added To List<String>

I have a List called dbData and two StringBuilders called infoSB and historySB. I've debugged my project and the two StringBuilders have all the data they are supposed to have, but for some reason it also adds some random characters to the data. All I've done to add the data is the code below:
dbData.add(infoSB.toString());
dbData.add(historySB.toString());
The characters being added are [ ] and ,
Has anyone ran into this before and know how to keep it from doing this?
UPDATE: Here is how I'm getting the data and assigning it to the StringBuilder.
JSONObject json_data = jArray.getJSONObject(i);
double altitudeData = json_data.getDouble("altitude");
double altitudeInFeet = altitudeData * 3.281;
historySB.append("Altitude: " + df.format(altitudeInFeet) + "ft\n");

Are these characters at the beginning and end of the string, and is the a comma somewhere in the middle? This is what the toStringmethod of List is meant to do.
If you have a list of three elements
"car"
"van"
"bike"
Then the list will create the following string [car, van, bike]. The [] denote the beginning and end of the list, and commas denote the boundary between elements.
If you just want to concatenate strings then either use the + operator or a StringBuilder / StringBuffer.
eg.
String data = infoSB + historySB;

- First Check your data source, does they carry some sort of odd characters you are receiving.
- I hope what those StringBuilder holds are not JSON, i suspected it cause you are getting [] and , in your StringBuilders , so if it does you need to parse them first and then need to retrieve the specific Data you want....
- You can avoid any dangling whitespaces using trim() method
Eg:
dbData.add(infoSB.toString().trim());
dbData.add(historySB.toString().trim());
///////////////////Edited Part///////////////////
DecimalFormat df = new DecimalFormat("##.###");
String altitudeData = json_data.getString("altitude");
double altitudeInFeet = Double.parseDouble(altitudeData) * 3.281;
historySB.append("Altitude: " + df.format(altitudeInFeet) + "ft\n");

Java - removing first character of a string

In Java, I have a String:
Jamaica
I would like to remove the first character of the string and then return amaica
How would I do this?

const str = "Jamaica".substring(1)
console.log(str)
Use the substring() function with an argument of 1 to get the substring from position 1 (after the first character) to the end of the string (leaving the second argument out defaults to the full length of the string).

public String removeFirstChar(String s){
return s.substring(1);
}

In Java, remove leading character only if it is a certain character
Use the Java ternary operator to quickly check if your character is there before removing it. This strips the leading character only if it exists, if passed a blank string, return blankstring.
String header = "";
header = header.startsWith("#") ? header.substring(1) : header;
System.out.println(header);
header = "foobar";
header = header.startsWith("#") ? header.substring(1) : header;
System.out.println(header);
header = "#moobar";
header = header.startsWith("#") ? header.substring(1) : header;
System.out.println(header);
Prints:
blankstring
foobar
moobar
Java, remove all the instances of a character anywhere in a string:
String a = "Cool";
a = a.replace("o","");
//variable 'a' contains the string "Cl"
Java, remove the first instance of a character anywhere in a string:
String b = "Cool";
b = b.replaceFirst("o","");
//variable 'b' contains the string "Col"

Use substring() and give the number of characters that you want to trim from front.
String value = "Jamaica";
value = value.substring(1);
Answer: "amaica"

You can use the substring method of the String class that takes only the beginning index and returns the substring that begins with the character at the specified index and extending to the end of the string.
String str = "Jamaica";
str = str.substring(1);

substring() method returns a new String that contains a subsequence of characters currently contained in this sequence.
The substring begins at the specified start and extends to the character at index end - 1.
It has two forms. The first is
String substring(int FirstIndex)
Here, FirstIndex specifies the index at which the substring will
begin. This form returns a copy of the substring that begins at
FirstIndex and runs to the end of the invoking string.
String substring(int FirstIndex, int endIndex)
Here, FirstIndex specifies the beginning index, and endIndex specifies
the stopping point. The string returned contains all the characters
from the beginning index, up to, but not including, the ending index.
Example
String str = "Amiyo";
// prints substring from index 3
System.out.println("substring is = " + str.substring(3)); // Output 'yo'

you can do like this:
String str = "Jamaica";
str = str.substring(1, title.length());
return str;
or in general:
public String removeFirstChar(String str){
return str.substring(1, title.length());
}

public String removeFirst(String input)
{
return input.substring(1);
}

The key thing to understand in Java is that Strings are immutable -- you can't change them. So it makes no sense to speak of 'removing a character from a string'. Instead, you make a NEW string with just the characters you want. The other posts in this question give you a variety of ways of doing that, but its important to understand that these don't change the original string in any way. Any references you have to the old string will continue to refer to the old string (unless you change them to refer to a different string) and will not be affected by the newly created string.
This has a number of implications for performance. Each time you are 'modifying' a string, you are actually creating a new string with all the overhead implied (memory allocation and garbage collection). So if you want to make a series of modifications to a string and care only about the final result (the intermediate strings will be dead as soon as you 'modify' them), it may make more sense to use a StringBuilder or StringBuffer instead.

I came across a situation where I had to remove not only the first character (if it was a #, but the first set of characters.
String myString = ###Hello World could be the starting point, but I would only want to keep the Hello World. this could be done as following.
while (myString.charAt(0) == '#') { // Remove all the # chars in front of the real string
myString = myString.substring(1, myString.length());
}
For OP's case, replace while with if and it works aswell.

You can simply use substring().
String myString = "Jamaica"
String myStringWithoutJ = myString.substring(1)
The index in the method indicates from where we are getting the result string, in this case we are getting it after the first position because we dont want that "J" in "Jamaica".

Another solution, you can solve your problem using replaceAll with some regex ^.{1} (regex demo) for example :
String str = "Jamaica";
int nbr = 1;
str = str.replaceAll("^.{" + nbr + "}", "");//Output = amaica

My version of removing leading chars, one or multiple. For example, String str1 = "01234", when removing leading '0', result will be "1234". For a String str2 = "000123" result will be again "123". And for String str3 = "000" result will be empty string: "". Such functionality is often useful when converting numeric strings into numbers.The advantage of this solution compared with regex (replaceAll(...)) is that this one is much faster. This is important when processing large number of Strings.
public static String removeLeadingChar(String str, char ch) {
int idx = 0;
while ((idx < str.length()) && (str.charAt(idx) == ch))
idx++;
return str.substring(idx);
}

##KOTLIN
#Its working fine.
tv.doOnTextChanged { text: CharSequence?, start, count, after ->
val length = text.toString().length
if (length==1 && text!!.startsWith(" ")) {
tv?.setText("")
}
}