Java--character arrays and strings, StringBuilder and string conversion

1. String-> Character array:

String str = “abc”；

char[] a = str.toCharArray();

Remember: String is a class, so use built-in functions

延伸 ： char b = str.charAt (1);

              str.length();

              a.length;

2. Character array-> String:

String str = String.valueOf(a)；

Memory: Similar to mandatory type conversion format, String (a)

Extension: character to character class

    Character c = Character.valueOf(a[1]);

3. Character array-> StringBuilder:

StringBuilder sb = new StringBuilder();

for(int i = 0; i < a.length; i++)

sb.append(a[i]);

Only hard conversion

4. String-> StringBuilder:

StringBuilder sb = new StringBuilder(str)

Memory: when initialized

5. StringBuilder-> String:

String str = sb.toString();

Memory: Like string to character array, built-in functions, pay attention to the brackets! Same as the string str.length ()

6. Delete StringBuilder

sb.delete (0, n)

Delete elements from 0 to n-1.