How to know if a given string is substring from another string in Java

Question

Hi I have to compute if a given string is substring of a bigger string. For example

String str = \"Hallo my world\";
String substr = \"my\"

<

Answer 1

 String str="hello world";
        System.out.println(str.contains("world"));//true
        System.out.println(str.contains("world1"));//false

• Javadoc

Answer 2

I think there is a String function that does just what you are asking: String.indexOf(String).

See this link: http://download.oracle.com/javase/1.4.2/docs/api/java/lang/String.html#indexOf(java.lang.String)

So, then you could write this function:

public boolean isSubstring(String super, String sub) {
    return super.indexOf(sub) >= 0;
}

Answer 3

*In their any sub string will be count by the form of 1th place of string of substring *

int isSubstring(string s1, string s2) {
    int M = s1.length();
    int N = s2.length();

    for (int i = 0; i <= N - M; i++) {
        int j;
        for (j = 0; j < M; j++)
            if (s2[i + j] != s1[j])
                break;

        if (j == M)
            return i;
    }

    return -1;
}


int main() {
    string s1 = "kumar";
    string s2 = "abhimanyukumarroy";
    int res = isSubstring(s1, s2);
    if (res == -1)
        cout << "Not present";
    else
        cout << "Present at index " << res;
    return 0;
}

Answer 4

here is a general method that you can use

public static boolean isSubstring(String s1, String s2) {
    if(s1.length() == s2.length()) 
        return s1.equals(s2);
    else if(s1.length() > s2.length())
        return s1.contains(s2);
    else
        return s2.contains(s1);

}