import java.nio.charset.StandardCharsets;

public class Main01 {

public static void main(String[] args) {

Main01.trans_type();

Main01.basic_string();

Main01.char_array();

Main01.utf8_byte();

Main01.basic_method();

Main01.string_builder();

}

public static void trans_type() {

System.out.println("\n#trans_type");

System.out.println("valueOf(int): " + String.valueOf(233));

System.out.println("valueOf(boolean): " + String.valueOf(true));

System.out.println("valueOf(object): " + String.valueOf(new Object()));

System.out.println("parseInt(int): " + String.valueOf(Integer.parseInt("233") - 1));

System.out.println("valueOf(String): " + String.valueOf(Integer.valueOf("233") + 1));

}

public static void basic_string() {

System.out.println("\n#basic_string");

System.out.println('A');

System.out.println((int) ('A'));

System.out.println("中");

System.out.println('\u0041');

System.out.println('\u4e2d'); // '中'

// System.out.println((int) ('中'));

String a = null;

System.out.println(a);

System.out.println("");

System.out.println("hello " + "world");

}

public static void char_array() {

System.out.println("\n#char_array");

System.out.println("hello".toCharArray());

char[] cs1 = { '2', '3', '3' };

System.out.println(new String(cs1));

}

public static void utf8_byte() {

System.out.println("\n#utf8_byte");

final byte[] bs1 = "hello".getBytes(StandardCharsets.UTF_8); // strange, Fail when use "UTF-8"

System.out.println(new String(bs1, StandardCharsets.UTF_8));

// System.out.println(new String("hello".getBytes("UTF-8"), "UTF-8"));

// System.out.println(new String("hello".getBytes("UTF-8"),

// StandardCharsets.UTF_8));

}

public static void basic_method() {

System.out.println("\n#basic_method");

String s1 = "hello", s2 = "Hello".toLowerCase();

String s3 = s1;

System.out.printf("s1==s2: %s; s1.equals(s2): %s \n", String.valueOf(s1 == s2), String.valueOf(s1.equals(s2)));

System.out.printf("s1==s3: %s; s1.equals(s3): %s \n", String.valueOf(s1 == s3), String.valueOf(s1.equals(s3)));

System.out.println(s1.contains("ll"));

System.out.println(s1.indexOf("ll"));

System.out.println(s1.indexOf("l"));

System.out.println(s1.lastIndexOf("l"));

System.out.println(s1.startsWith("he"));

System.out.println(s1.endsWith("he"));

System.out.println(" \t\r\nhello\n\r\t".trim());

System.out.println("hello world".substring(2, 4));

System.out.println("hElLo WoRlD".toUpperCase().toLowerCase());

System.out.println("hello world".replace('l', 'L'));

System.out.println("hello world".replace("ll", "LL"));

System.out.println(String.join("~", "A,,B;C ,D".split("[,; ]+")));

}

public static void string_builder() {

System.out.println("\n#string_builder");

StringBuilder z1 = new StringBuilder(128);

for (int i = 0; i < 100; i++) {

z1.append(String.valueOf(i));

}

System.out.println(z1.toString());

StringBuilder z2 = new StringBuilder(128);

System.out.println(z2.append("Mr ").append("233").append("!").insert(0, "Hello, ").toString());

}

}