Some core content of strings in Java

first, thecommon method of StringBuilder class in Java

Append (parameter): Append content to the end of the current StringBuilder object

Insert (position, parameter): Inserts the content into the specified position of the StringBuilder object

ToString (): Converts a StringBuilder object to a String object

Length (): Gets the length of the string

toLowerCase (): Convert to lowercase

charAt (int i): Gets the value indexed to I

GetBytes (): Convert to byte array

indexOf (int ch): Find the ch character where the string first appears

IndexOf (String str): Find the first occurrence of the STR string in the position of the string

Lastindexof (int ch): Find the CH character at the last occurrence of the string

LastIndexOf (String str): Finds the position of the STR string at the last occurrence of the string

Split (): Splits the string into substrings;

1 "Append and insert operations for StringBuilder objects

1 StringBuilder str=new StringBuilder ("Hello"); 2 str.append ("World"); 3 str.append ("!") ); 4 System.out.println (Str.length ()); 5 System.out.println (str);
6 Str.insert (12. "!");
7 Sting str2=str.tostring ();
8 System.out.println ("After insertion:" +STR2);

Output Result: 12

Hello world!

After insertion: Hello world!!

Note : StringBuffer and StringBuilder function the same, but StringBuffer is thread-safe, and StringBuilder does not implement thread-safe functionality, so performance is slightly higher. Therefore, in general, if you need to create a variable-content string object, you should consider using the StringBuilder class as a priority.

Second,"= =" and equals () What is the difference?

= =: 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

1 String str1= "I love You"; 2 string str2=new string ("I Love You"); 3 System.out.println ("str1 and str2 have the same memory address?") "+ (str1==str2)); 4 System.out.println ("str1 and str2 have the same content? "+str1.equals (STR2));

Output Result: false

True

Some core content of strings in Java