Suppose, there is a requirement to check that a particular string is present in a file but with a restriction that it should only be present between a pair of string. For example the string “your age” should be present in between “What is” and “?”.
Working code follows:
/*
* Just pass a String array with necessary parameters and you are good to go
*/
public boolean verifyTextPresence(String[] params)
throws FileNotFoundException {
String filePath = params[0];
//string before the string to check
String startStr = params[1];
//string after the string to check
String endStr = params[2];
//string to find
String strToCheck = params[3];
boolean isStrPresent = false;
Scanner scan = null;
try {
scan = new Scanner(new File(filePath));
boolean isStartTag = false;
while (scan.hasNextLine()) {
String line = scan.nextLine();
int startIndex = 0, endIndex=0;
if (line.contains(startStr)) {
// string flag to indicate that start string has been found
isStartTag = true;
startIndex = line.indexOf(startStr);
}
// we need to check that the end string is present and
// it occurs after the start string, not before it
if(isStartTag && line.contains(endStr)){
// get the location of end string
endIndex = line.indexOf(endStr, startIndex);
// check if the string to find exists between the start and end strings
if(line.substring(startIndex, endIndex).contains(strToCheck)){
isStrPresent = true;
//terminate loop if the string has been found in a line
break;
}
}
}
if (isStrPresent) {
System.out.println("String \"" + strToCheck
+ "\" is present between the start and end strings \""
+ startStr + "\" and \"" + endStr + "\" respectively");
return true;
}
//print error message if the string cannot be found
String errMesg = "String \"" + strToCheck
+ "\" is NOT present between the start and end strings \""
+ startStr + "\" and \"" + endStr + "\" respectively";
System.out.println(errMesg);
} catch (FileNotFoundException fne) {
throw fne;
} finally {
if(scan!=null){
scan.close();
}
}
return false;
}
Let’s tweak in:
1. Always catch FileNotFoundException when dealing with files.
2. Close the scanner object in finally block. Starting java 7 this may be avoided if try-with-resources statement is used in which the resources are automatically closed.
