To check whether a particular String a is being contained in a String b or not, we can use the method [String.contains()](<https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#contains-java.lang.CharSequence->) with the following syntax:
b.contains(a); // Return true if a is contained in b, false otherwise
The [String.contains()](<https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#contains-java.lang.CharSequence->) method can be used to verify if a CharSequence can be found in the String. The method looks for the String a in the String b in a case-sensitive way.
String str1 = "Hello World";
String str2 = "Hello";
String str3 = "helLO";
System.out.println(str1.contains(str2)); //prints true
System.out.println(str1.contains(str3)); //prints false
To find the exact position where a String starts within another String, use [String.indexOf()](<https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#indexOf-java.lang.String->):
String s = "this is a long sentence";
int i = s.indexOf('i'); // the first 'i' in String is at index 2
int j = s.indexOf("long"); // the index of the first occurrence of "long" in s is 10
int k = s.indexOf('z'); // k is -1 because 'z' was not found in String s
int h = s.indexOf("LoNg"); // h is -1 because "LoNg" was not found in String s
The [String.indexOf()](<https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#indexOf-java.lang.String->) method returns the first index of a char or String in another String. The method returns -1 if it is not found.
Note: The [String.indexOf()](<https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#indexOf-java.lang.String->) method is case sensitive.
Example of search ignoring the case:
String str1 = "Hello World";
String str2 = "wOr";
str1.indexOf(str2); // -1
str1.toLowerCase().contains(str2.toLowerCase()); // true
str1.toLowerCase().indexOf(str2.toLowerCase()); // 6