Introduction to ApiDemo in java

I have been playing "Airplane War" for a while, and will make up the complete code for Airplane War later.

Hurry up and continue the follow-up course

API String related methods:

Note: When it comes to intercepting/deleting/inserting string positions, it refers to the position of the subscript x; if If it is a range, the head will be taken without the tail.

 1 package com.jookersight; 2  3 public class ApiDemo { 4     public static void main(String[] args){ 5         /** 6          * String的多个方法 7          * 包括：indexof,lastindexof,substring 8          */ 9 10         String str = "123strssss";11         String str1 = "123"+"strssss";12         String str2 = new String("123strssss");13 14         System.out.println(str == str1);  //true,相等 对于引用类型,指的是引用对象的地址相同15         System.out.println(str == str2);  //false16         System.out.println(str.equals(str2));  //equals 指的是 对于引用类型,内容相同17 18         /**19          * indexof/lastindexof20          * 检索字符串在目标字符串中首次/末次出现位置21          */22         int index = str.indexOf("tr");23         System.out.println(index);24         int index1 = str.indexOf("rs",4);  //从下标4开始第一次出现的rs在字符串中的位置25         int index2 = str.lastIndexOf('s');  //字符'xxx'&字符串"xxx"在字符串中最后一次出现的位置26         System.out.println(index1);27         System.out.println(index2);28 29         /**30          * substring(int beginindex,int endindex)  截取字符串31          * toUpperCase()  字符串全大写32          * toLowerCase()  字符串全小写33          */34         String str3 = "this is a world of mine";35         String a = str3.substring(3,7);  //截取下标[3,7)36         System.out.println(a);37         String str4 = "JavainDex";38         String s = str4.toUpperCase();  //全字符串大写39                                         //toLowerCase()  全字符串小写40         System.out.println(s);  //JAVAINDEX41 42 43         /**44          * StringBuilder45          * 频繁修改字符串46          */47         String str5 = "123";48         StringBuilder builder = new StringBuilder();49 50         builder.append(str5);  // *添加字符串源51         builder.append(456);  //追加52         builder.delete(0,2);  //删除，[0,2)  345653         builder.replace(0,2,"78");  //替换  785654         builder.insert(3,'a');  //插入,在下标x处之前插入字符串、字符55         str5 = builder.toString();  //合并成一个字符串56 57         System.out.println(str5);  //785a658     }59 }

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