You can achieve this in 2 different ways...
- The old school
 
- and the lambdas way
 
Old school  Example:
public static void main(String[] args) {
    List<String> abc = new ArrayList<>();
    abc.add("hi");
    abc.add("hello Yash");
    abc.add("i am Yash");
    String x = "Yash";
    List<String> resultOldSchool = new ArrayList<>();
    for (String sentence : abc) {
        if (sentence.contains(x)) {
            resultOldSchool.add(sentence);
        }
    }
    System.out.println(resultOldSchool);
}
Lambdas way Example:
public static void main(String[] args) {
    List<String> abc = new ArrayList<>();
    abc.add("hi");
    abc.add("hello Yash");
    abc.add("i am Yash");
    String x = "Yash";
    List<String> resultJava8 = findStringInList(abc, x);
    if (!resultJava8.isEmpty()) {
        System.out.println(resultJava8);
    }
}
public static List<String> findStringInList(final List<String> list, final String strng) {
    return list.stream().filter(s -> s.contains(strng)).collect(Collectors.toList());
}
feel free to decide....