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I want to convert weird characters to normal in Java

I'm dealing with Java and I want to convert a String like this:
String = "SAYILI BU�DAYLI TARIM KREDİ KOOPERATİFİ"
to
SAYILI BUĞDAYLI TARIM KREDİ KOOPERATİFİ
as output. How can I do that?

You have non printable characters in your input string
String str = "SAYILI BU�DAYLI TARIM KREDİ KOOPERATİFİ";
Normalizer.normalize(str, Normalizer.Form.NFD);
str = str.replaceAll("[^\\x00-\\x7F]", "");
System.out.println(str);
This will remove the non printable characters from you string
output string will be SAYILI BUDAYLI TARIM KRED KOOPERATF

Java String TRIM function not working

I am receiving a string from server trailing one or two lines of spaces like below given string.
String str = "abc*******
********";
Consider * as spaces after my string
i have tried a few methods like
str = str.trim();
str = str.replace(String.valueOf((char) 160), " ").trim();
str = str.replaceAll("\u00A0", "");
but none is working.
Why i am not able to remove the space?

You should try like this:
str = str.replaceAll("\n", "").trim();
You can observe there is a new line in that string . first replace new line "\n" with space("") and than trim

You should do:
str = str.replaceAll("\n", "");
In my case use to work the function trim()

Try this:
str = str.replaceAll("[.]*[\\s\t]+$", "");

I have tried your 3 methods, and them all work. I think your question describing not correctly or complete, in fact, a String in java would not like
String str = "abc*******
********";
They must like
String str = "abc*******"
+ "********";
So I think you should describe your question better to get help.

Removing leading NewLine chars from String by regex?

I am new to "REGEX".And this question is training and educational for regex in java.
I try to remove leading new line chars from a string.(I know we can do this by 'trim()',but I do not want use it).I use '^[\r\n]+' as regex,like this:
str = "\r\n\r\ntest";
str.replaceAll("^[\r\n]+", "");
System.out.print(str);
I guess result will be
test
But the result is:
CRLF
CRLF
test
As you can see,leading new line chars do not removed.Also I try '^\s' or '^\s+' as regex,but result was same.Do you know why those regexes do not match leading new line chars?

A String cannot be modified: replaceAll returns the changed string.
str = str.replaceAll(...);

Java - New Line Character Issue

I have a code like,
String str = " " ;
while( cond ) {
str = str + "\n" ;
}
Now, I don't know why at the time of printing, the output string is not printing the newline character. However, when I add any other character like ( str = str + "c"), it is printing properly. Can anybody help me, how to solve this problem and why this happening ?

The newline character is considered a control character, which doesn't print a special character to the screen by default.
As an example, try this:
String str = "Hi";
while (cond) {
str += "\n"; // Syntactically equivalent to your code
}
str += "Bye";
System.out.println(str);

Looks like you are trying to run the above code on Windows. Well the line separator or new line is different on Windows ( '\r\n' ) and Unix flavors ('\n').
So, instead of hard coding and using '\n' as new line. Try getting new line from the system like:
String newLine = System.getProperty("line.separator");
String str = " " ;
while( cond ) {
str = str + newLine ;
}

If you really want \n, to get printed, do it like this.
String first = "C:/Mine/Java" + "\\n";
System.out.println(first);
OUTPUT is as follows :
For a good reference as to why is this happening, visit JAVA Tutorials
As referred in that TUTORIAL : A character preceded by a backslash is an escape sequence, and has a special meaning to the compiler. When an escape sequence is encountered in a print statement, the compiler interprets it accordingly
Hope this might help.
Regards

Based on your sample, the only reason it would not show a new line character is that cond is never true and thus the while loop never runs...

Is there a Java function which parses escaped characters?

I'm looking for a built-in Java functions which for example can convert "\\n" into "\n".
Something like this:
assert parseFunc("\\n") = "\n"
Or do I have to manually search-and-replace all the escaped characters?

You can use StringEscapeUtils.unescapeJava(s) from Apache Commons Lang. It works for all escape sequences, including Unicode characters (i.e. \u1234).
https://commons.apache.org/lang/apidocs/org/apache/commons/lang3/StringEscapeUtils.html#unescapeJava-java.lang.String-

Anthony is 99% right -- since backslash is also a reserved character in regular expressions, it needs to be escaped a second time:
result = myString.replaceAll("\\\\n", "\n");

Just use the strings own replaceAll method.
result = myString.replaceAll("\\n", "\n");
However if you want match all escape sequences then you could use a Matcher. See http://www.regular-expressions.info/java.html for a very basic example of using Matcher.
Pattern p = Pattern.compile("\\(.)");
Matcher m = p.matcher("This is tab \\t and \\n this is on a new line");
StringBuffer sb = new StringBuffer();
while (m.find()) {
String s = m.group(1);
if (s == "n") {s = "\n"; }
else if (s == "t") {s = "\t"; }
m.appendReplacement(sb, s);
}
m.appendTail(sb);
System.out.println(sb.toString());
You just need to make the assignment to s more sophisticated depending on the number and type of escapes you want to handle. (Warning this is air code, I'm not Java developer)

If you don't want to list all possible escaped characters you can delegate this to Properties behaviour
String escapedText="This is tab \\t and \\rthis is on a new line";
Properties prop = new Properties();
prop.load(new StringReader("x=" + escapedText + "\n"));
String decoded = prop.getProperty("x");
System.out.println(decoded);
This handle all possible characters