Detailed explanation of string's trim() and substring()

trim() Method :

substring() Method :

If substring() Write only one parameter in the method :

trim() Method :

give an example :

        String str = "  32143243 2 ";
        System.out.println(str.trim());

Output ( Remove the spaces at the beginning and end ):
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If there are spaces at the beginning or end of a string , Call substring() Cut it off ;
If there is no space , Then return the string

substring() Method :

give an example :

        String str = "321432432";
        System.out.println(str.substring(0,3));

Output ( Intercepted subscript 0-3 Substring of ):
Check the source code for analysis

When the input start index and end index do not meet the conditions , Throw an exception ;
When entering the start index =0 And when the end index is equal to the length of the string , Returns the original string ;
otherwise new One String object ( Address change )

If substring() Write only one parameter in the method :

        String str = "321432432";
        System.out.println(str.substring(3));

Output ( Intercepted subscript 3 Numbers to the end ):

Check the source code for analysis :

When writing only one starting index :
Less than 0, disqualification , Throw an exception ;
Start to compare the index with the string length , If the difference is less than 0, Throw an exception ;
If the difference is greater than 0, Start with this index , The length of the string is the end index new One String object