String common API

String Commonly used API

1、public int length​() Returns the length of this string
2、public char charAt​(int index) Get the character at an index position
3、public char[] toCharArray​()： Converts the current string into a character array and returns
4、public String substring(int beginIndex, int endIndex) Intercept according to the start and end indexes , Get the new string （ Not before, not after ）
5、public String substring(int beginIndex) Intercept from the incoming index , Intercept to the end , Get the new string
6、public String replace(CharSequence target,
7、CharSequence replacement) Use new value , Replace the old value in the string with , Get the new string
9、public String[] split(String regex) Cut the string according to the incoming rules , Get string array return

/* * String Commonly used API * */
public class StringDemo4 {
    
    public static void main(String[] args) {
    

        //public int length()  Returns the length of this string 
        String name = " I love you China love";
        System.out.println(name.length());

        //public char charAt(int index)  Get the character at an index position 
        char c = name.charAt(1);
        System.out.println(c);

        System.out.println("----------- Each character in the convenience string -----------");
        for (int i = 0; i < name.length(); i++) {
    
            char ch = name.charAt(i);
            System.out.println(ch);
        }

        //public char[] toCharArray()：  Converts the current string into a character array and returns 
        System.out.println("----------- String into character array -----------");
        char[] chars = name.toCharArray();
        for (int i = 0; i < chars.length; i++) {
    
            char ch = chars[i];
            System.out.println(ch);
        }


        //public String substring(int beginIndex, int endIndex)  Intercept according to the start and end indexes , Get the new string （ Not before, not after ）
        String name2 = "Java Is the most powerful programming language ！";
        String rs = name2.substring(0, 9);
        System.out.println(rs);


        //public String substring(int beginIndex)  Intercept from the incoming index , Intercept to the end , Get the new string 
        String rs1 = name2.substring(4);
        System.out.println(rs1);

        //public String replace(CharSequence target,CharSequence replacement) Use new value , Replace the old value in the string with , Get the new string 
        String name3 = " Zhang San is the most powerful 80 after , Zhang sanbang ！";
        String rs3 = name3.replace(" Zhang San ", "***");
        System.out.println(rs3);

        //public boolean contains(CharSequence s)
        System.out.println(name3.contains(" Zhang San "));//true
        System.out.println(name3.contains(" Zhang Er "));//false

        //public boolean startsWiths(String prefix)// With "prefix" At the beginning 
        name3.startsWith(" Zhang San ");//true

        //public String[] split(String regex)  Cut the string according to the incoming rules , Get string array return 
        String name4 = " Zhang San , Li Si , Liu Wu ";
        String[] names = name4.split(",");
        for (int i = 0; i < names.length; i++) {
    
            System.out.println(" I chose ：" + names[i]);
        }
    }
}