Extracting value from a string in java

Question

I have a string, and I want to extract the text abcd from this string. I useed the indexOf() method to get the start index, but how we can I set the end index value? The abcd text value is dynamic, so we can't hardcode it like startIndex()+5. I need some logical code.

String str = "Hi Welcome to stackoverflow : " +"\n"+"Information :"+"\n"+"hostname : abcd"+"\n"+
"questiontype : text"+"value : desc.";

if(str.contains("hostname : "))
{
String value = "hostname : "
int startIndex = str.indexof("hostname : ") + value.length();
// how to find the endIndex() in that case
}

These may be useful: String::substring, String::indexOf, String::length. — MC Emperor
– MC Emperor, Commented Dec 15, 2020 at 12:36
You can look for what comes after the abcd-value and use this information to get an endIndex. — Ralf Renz
– Ralf Renz, Commented Dec 15, 2020 at 12:38
How to find the end index? The question is the answer: it depends on what defines the end of the text. — Kevin Anderson
– Kevin Anderson, Commented Dec 15, 2020 at 12:40
You can't really know how long the remaining value is, unless you specify a structure to which this text conforms. It seems that after each value, a newline is present, so you could simply search for the newline after the key with str.substring(startIndex, str.indexOf("\n", startIndex)). — MC Emperor
– MC Emperor, Commented Dec 15, 2020 at 12:43

TimonNetherlands · Accepted Answer · 2020-12-15 12:43:26Z

2

String answer = str.substring( str.indexOf( value) + value.length(), str.indexOf( "questiontype :" ) );

answered Dec 15, 2020 at 12:43

TimonNetherlands

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user157629 · Accepted Answer · 2020-12-15 12:53:37Z

0

If you want to get the string after "hostname : " you can do:

String str = "Hi Welcome to stackoverflow : " +"\n"+"Information :"+"\n"+"hostname : abcde"+"\n"+
        "questiontype : text"+"value : desc.";
    

int startIndex = str.indexOf("hostname") + "hostname : ".length();
int endIndex = str.indexOf("questiontype") - 1;

String result = str.substring(startIndex, endIndex);

System.out.println(result);

Also note that you can add \n to the text of the string without needing to append it so that: "Hi Welcome to stackoverflow : " +"\n"+"Information..." would work just as fine doing: "Hi Welcome to stackoverflow : \nInformation..."

edited Dec 15, 2020 at 12:53

answered Dec 15, 2020 at 12:44

user157629

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Joop Eggen · Accepted Answer · 2020-12-15 15:11:59Z

0

Perhaps not as efficient as the answers with indexOf, a regex solution is succint.

Optional<String> getValue(String properties, String keyName) {
    Pattern pattern = Pattern.compile("(^|\\R)" + keyName + "\\s*:\\s*(.*)(\\R|$)");
    Matcher m = pattern.matcher(properties);
    return m.find() ? Optional.of(m.group(2)) : Optional.emtpy();
}

String hostname = getValue("...\nhostname : abc\n...", 
                           "hostname").orElse("localhost");

edited Dec 15, 2020 at 15:11

answered Dec 15, 2020 at 15:03

Joop Eggen

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