Search string in file and return next line (in Java)

Question

As my title says. I need to search through a file for a string. When its found, I need the next line. It's a file like this:

hello

world

When "hello" is found, "world" needs to be returned.

File file = new File("testfile");
Scanner scanner = null;
try {
  scanner = new Scanner(file);
} catch (FileNotFoundException e) {
  e.printStackTrace();
}

if (scanner != null) {
  String line;
  while (scanner.hasNextLine()) {
    line = scanner.nextLine();
    if (line == "hello") {
      line = scanner.nextLine();
      System.out.println(line);
    }
  }
}

It reads through the file but it doesn't find the word "hello".

possible duplicate of [How do I compare strings in Java?](http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java) — jlordo, Feb 23 '13 at 20:17

score 5 · Accepted Answer · answered Feb 23 '13 at 20:01

5

if (line == "hello") {

should be

if ("hello".equals(line)) {

You have to use equals() method to check if two string objects are equal. == operator in case of String(and all objects) only checks if two reference variables refer to the same object.

answered Feb 23 '13 at 20:01

PermGenError

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score 1 · Answer 2 · edited Dec 09 '13 at 14:10

1

if (line == "hello")

should be changed to

if (line.contains("hello"))

edited Dec 09 '13 at 14:10

Sk8erPeter

6,899
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answered Jun 28 '13 at 07:01

Vicky

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score 0 · Answer 3 · answered Jun 12 '15 at 09:02

0

Instead of using == operator to compare two strings use if(line.compareTo("hello") == 0)

answered Jun 12 '15 at 09:02

Search string in file and return next line (in Java)

3 Answers3