What does indexOf in java mean?

indexOf in java represents the index. It can find characters in a given string and return the subscript corresponding to the character. If it is not found, it returns [-1].

indexOf has four usages:

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1.indexOf(int ch)

Search for characters (ASCII) in the given string, find the subscript corresponding to the returned character array and cannot find the return - 1

2.indexOf(String str)

Find another string in the given string.

3.indexOf(int ch,int fromIndex)

Returns the index of the first occurrence of the specified character in the string, if there is no such occurrence in this string characters, returns -1.

4.indexOf(String str,int fromIndex)

Returns the index of the first occurrence of the specified character in the string starting from the fromIndex position. If this If there is no such character in the string, -1 is returned.

Syntax

public int indexOf(int ch )

或

public int indexOf(int ch, int fromIndex)

或

int indexOf(String str)

或

int indexOf(String str, int fromIndex)

Parameters

• ch -- Character, Unicode encoding.

• fromIndex -- The index position where the search starts. The first character is 0, the second is 1, and so on.

• #str -- The substring to search for.

Return value

• Find the string, or the position where the character Unicode encoding appears in the string:

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