Java Basics: Case conversion of string, separation of array, = = vs. equals ()

Continue to look at the commonly used methods of the String class, as shown in the following code:

Operation Result:

So,what is the difference between "= =" and equals ()?

= =: Determines whether the first address in memory of two strings is the same, that is, whether it is the same string object

Equals (): Compares the content stored in two string objects in a consistent

PS: Bytes is the basic unit of computer storage information,1 bytes equals 8 bits , 1 characters stored in GBK encoding need 2 bytes ,1 English characters storage requires 1 bytes . So we see the above program running results, each Chinese character corresponds to two byte values, such as "learn" corresponding to "47-89", while the English letter "J" corresponds to "74". At the same time, we also found that the Chinese characters corresponding to the byte value is negative, because each byte is 8 bits, the maximum value can not exceed 127, and the Chinese character converted to a byte after more than 127, if more than will overflow, in the form of negative numbers display.

Case:

Function: Count the number of occurrences of the character ' a ' in the specified string

Analysis: You can iterate through each character in a string to determine if it is a character a, and if so, the number of occurrences of the cumulative statistic

1  Public classHelloWorld {2      Public Static voidMain (string[] args) {3         //Define a string4String s = "ALJLKDSFLKJSADJFKLHASDKJLFLKAJDFLWOIUDSAFHAASDASD";5         6         //Number of occurrences7         intnum = 0;8         9          //Loop through each character to determine if it is a character a, and if so, the number of incrementsTen          for(intI=0;i<s.length (); i++) One         { A             //gets each character, judging whether it is a character a -             if(S.charat (i) = = ' A ') { -                 //Cumulative Statistics Number thenum++;  -             } -         } -System.out.println ("The number of occurrences of character A:" +num); +     } -}

Java Basics: Case conversion of string, separation of array, = = vs. equals ()