Java common string method summary

The following is a brief summary of the code for string manipulation. Most are String class operation method, need friends can refer to below

public class StudyString {
    public static void main(String[] ergs){
        // String declaration and assignment 
        String name = " Cai Yufei ";
        String hisname = new String (" Xiao Ming ");
        System.out.println(name+" and "+hisname+" It is a good friend ");
        // String basic operation 
        // Gets the length of the string 
        // String name .length()  Returns the number of characters 
        String hello = "hello world!";
        int length = hello.length();
        System.out.println(hello+" Is the length of the "+length);
        // String concatenation 
        //String Class provides the concat() methods 
        // string 1.concat( string 2)  The return value is 1 A string 
        String twoname = name.concat(hisname);
        System.out.println(twoname);
    // String comparison 
        //String To provide the equals() Method with a return value of boolean Type. Two strings in each character are complete 1 For the cause turn. Otherwise, for false
        // string 1.equals( string 2)
        String str1 = "fuck";
        String str2 = "FUCK";
        if (str1.equals(str2))
            System.out.println(" The same ");
        else
            System.out.println(" different ");
        //String Also provides equalsIgnoreCase() Method, which differs from the above one in that it is case-insensitive. The return value is the same boolean type 
        // string 1.equalsIgnoreCase( string 2)
        if(str1.equalsIgnoreCase(str2))
            System.out.println(" The same ");
        else
            System.out.println(" different ");
   // String interception 
        // Extract from a string 1 Part as a new string, String Class provides the substring To implement the 
        // string .substring ( The starting position );  or    string .substring ( The starting position , End position );
        // The first 1 The species is from the beginning to the end, no 2 Species from the beginning to the end .
        String my ="my name is caiyufei,I love Java and Python.";
        String love =my.substring(20); 
        String myname = my.substring(11, 19);
        System.out.println(love);
        System.out.println(myname);
        // String lookup 
        // in 1 Find another in a string 1 A string of, String Class provides a indexOf Method to implement 
        // string 1.indexOf( string 2)  or    string 1.indexOf( string 2, The starting position )
        int lovenum = my.indexOf(love);
        int mynamenum = my.indexOf(myname);
        System.out.println(lovenum);
        System.out.println(mynamenum);
        // String substitution 
        // with 1 Three new characters to replace all the characters specified in the string  String Class provides a replace Method to implement this substitution 
        // string 1.replance( Substituted character , Substitution characters )
        char I_ = 'I';
        char m_ = 'M';
        System.out.println(love.replace(I_, m_)); //M love Java and Python.
  // String and character arrays 
        // Converts an array of characters directly to a string as an argument to the constructor 
        char [] helloArray = {'h','e','l','l','o'};
        String helloString = new String (helloArray);
        System.out.println(helloString);
        // Converts a string to an array of characters 
        //toCharArray() methods 
        char [] Array = helloString.toCharArray();
        for (int i = 0;i<Array.length;i++)
            System.out.println(Array[i]);
        // Other methods 
        // Chinese and English characters are converted to lowercase characters 
        String eng = "I Love English";
        String eng_1 = eng.toLowerCase();
        System.out.println(eng_1);
        // The Chinese and English characters of the string are capitalized 
        String eng_2 = eng.toUpperCase();
        System.out.println(eng_2);
        // Returns the character at the specified index 
        char en = eng.charAt(5);
        System.out.println(en);//e
        // Compare strings, return int
        int num_1 = eng.compareTo(eng_1);
        System.out.println(num_1);
 // Returns the first 1 The position of the substring found, or none -1
        String loves = "Love";
        int lovenum1 = eng.indexOf(loves);
        System.out.println(lovenum1); //2
        // Removes Spaces before and after the string 
        String world = "   I love my world   ";
        System.out.println(world);
        world = world.trim();
        System.out.println(world);
        // judge suffix Is the beginning of a string 
        String suffix = "world";
        if (world.startsWith(suffix))
            System.out.println("world Is the string world The beginning of the ");
        else
            System.out.println("world Not a string world The beginning of the ");
  // judge suffix Is the end of the string 
        if (world.endsWith(suffix))
            System.out.println("world Is the string world At the end of the ");
        else
            System.out.println("world Not a string world At the end of the ");
        //String buffer  class 
        // Greatly improves the processing speed of strings, but the disadvantage is that it takes up a lot of memory. Used when dealing with extremely large Numbers of characters 
        StringBuffer sb = new StringBuffer("StringBuffer beautifer good");
        System.out.println(sb);
        // Add parameters to StringBuffer In the object 
        sb.append(",");
        sb.append("I love StringBuffer!");
        System.out.println(sb);
        // delete StringBuffer Specifies a character or sequence of characters in the 
        sb.deleteCharAt(0);// Deleting the location specified 1 A character 
        System.out.println(sb);
        sb.delete(0, 12);// Delete from one place to another 
        System.out.println(sb);
        //
    }
}

The above code learning friends can refer to