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String str = "Java Jives, Java Jives Java"; int i4 = str.indexOf("Jives", 4); int i5 = str.lastIndexOf("Jives", 5); System.out.println(i4); System.out.println(i5); The output is 5 and 5.Can anynody explain the output?
indexOf(String str, int fromIndex) Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. "Jives" is found at index 5 so the output is 5. If you set the fromIndex as 5 above, it still returns 5.
lastIndexOf(int ch, int fromIndex) Returns the index within this string of the last occurrence of the specified character, searching backward starting at the specified index. Begins to search backward from index 5 but since "Jives" is found at index 5, it returns 5. If you set the fromIndex as 4, "Jives" is not found hence returns -1. I was confused by looking at the code too, but after running the code with different index values, I arrived at this conclusion.
hi, Smith this kind of problem you can take a look of API doc. i try to explain: first, indexOf() is search from start and lastIndexOf() is search from end. second, indexOf() is find the lowest value as str.startWith("Jives", 4) && k>=4(according to doc ), so find String str is "Jives, Java Jives Java" and result is 5; lastIndexOf() is find the largest value as str.startWith("Jives", 5) && k<=5, so find String str is "Java J", it can find at positoin 5->J, so result is 5; hop this can help michael