Java Challenge - doubleX - warm_up_2

Given a string, return true if the first instance of "x" in the string is immediately followed by another "x".

doubleX("axxbb") → true
doubleX("axaxax") → false
doubleX("xxxxx") → true

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boolean doubleX(String str) { if(str.length() > 1) { int i = str.indexOf("x"); if(i < str.length()-1) { char l = str.charAt(i+1); if(l == 'x')return true; } } return false; }

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boolean doubleX(String str) { int i = str.indexOf("x"); if (i == -1) return false; // no "x" at all // Is char at i+1 also an "x"? if (i+1 >= str.length()) return false; // check i+1 in bounds? return str.substring(i+1, i+2).equals("x"); // Another approach -- .startsWith() simplifies the logic // String x = str.substring(i); // return x.startsWith("xx"); }

Java Challenge - countXX - warm_up_2

Count the number of "xx" in the given string. We'll say that overlapping is allowed, so "xxx" contains 2 "xx".

countXX("abcxx") → 1
countXX("xxx") → 2
countXX("xxxx") → 3

Solution :

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int countXX(String str) { int count = 0; for (int i = 0; i < str.length()-1; i++) { if (str.substring(i, i+2).equals("xx")) count++; } return count; }