Java Coding Problems Second Edition --chapter 01

第一章

1、节字符串连接

1、在jdk 8之前版本，可以使用 + 连接字符串

2、StringBuilder 进行append操作

3、string.concat进行操作

4、string format进行插空

5、jdk 8 s可以使用String ,join 进行字符串连接

6、java.util.StringJoiner 操作

7、使用 StringJoiner

8、 using Collectors#joining()

9、Starting with JDK 13/15using text blocks

package chaptor01.P01_TextBlockSQLJSONHTML;
 
import java.util.StringJoiner;
import java.util.stream.Collectors;
import java.util.stream.Stream;
 
public class Main {
    public static void main(String[] args) {
        //字符串连接
        // 在jdk 8 之前，我们使用+进行字符串连接
        System.out.println("Multiline SQL/JSON/HTML before text blocks "
                + "(using concatenation via the '+' operator):");
        String sql1
                = "UPDATE \"public\".\"office\"\n"
                + "SET (\"address_first\", \"address_second\", \"phone\") =\n"
                + "  (SELECT \"public\".\"employee\".\"first_name\",\n"
                + "          \"public\".\"employee\".\"last_name\", ?\n"
                + "   FROM \"public\".\"employee\"\n"
                + "   WHERE \"public\".\"employee\".\"job_title\" = ?";
 
        String json1
                = "{\n"
                + "  \"widget\": {\n"
                + "    \"debug\": \"on\",\n"
                + "    \"window\": {\n"
                + "      \"title\": \"Sample Widget 1\",\n"
                + "      \"name\": \"back_window\"\n"
                + "    },\n"
                + "    \"image\": {\n"
                + "      \"src\": \"images\\sw.png\"\n"
                + "    },\n"
                + "    \"text\": {\n"
                + "      \"data\": \"Click Me\",\n"
                + "      \"size\": 39\n"
                + "    }\n"
                + "  }\n"
                + "}";
 
        String html1
                = "\n"
                + "  
\n"
                + "    
\n"
                + "    
\n"
                + "  
\n"
                + "  
\n"
                + "    
\n"
                + "    
\n"
                + "    
\n"
                + "  
\n"
                + "
Name
Age
John
Smith
22
";
 
        System.out.println(sql1);
        System.out.println();
        System.out.println(json1);
        System.out.println();
        System.out.println(html1);
 
        // 我们同样可以 StringBuilder 连接 append 连接
        System.out.println("\n Multiline SQL/JSON/HTML before text blocks (using StringBuilder):");
        StringBuilder sql2 = new StringBuilder();
        sql2.append("UPDATE \"public\".\"office\"\n")
                .append("SET (\"address_first\", \"address_second\", \"phone\") =\n")
                .append("  (SELECT \"public\".\"employee\".\"first_name\",\n")
                .append("          \"public\".\"employee\".\"last_name\", ?\n")
                .append("   FROM \"public\".\"employee\"\n")
                .append("   WHERE \"public\".\"employee\".\"job_title\" = ?;");
 
        StringBuilder json2 = new StringBuilder();
        json2.append("{\n")
                .append("  \"widget\": {\n")
                .append("    \"debug\": \"on\",\n")
                .append("    \"window\": {\n")
                .append("      \"title\": \"Sample Widget 1\",\n")
                .append("      \"name\": \"back_window\"\n")
                .append("    },\n")
                .append("    \"image\": {\n")
                .append("      \"src\": \"images\\sw.png\"\n")
                .append("    },\n")
                .append("    \"text\": {\n")
                .append("      \"data\": \"Click Me\",\n")
                .append("      \"size\": 39\n")
                .append("    }\n")
                .append("  }\n")
                .append("}");
 
        StringBuilder html2 = new StringBuilder();
        html2.append("
\n")
                .append("  
\n")
                .append("    
\n")
                .append("    
\n")
                .append("  
\n")
                .append("  
\n")
                .append("    
\n")
                .append("    
\n")
                .append("    
\n")
                .append("  
\n")
                .append("
Name
Age
John
Smith
22
");
 
        System.out.println(sql2);
        System.out.println();
        System.out.println(json2);
        System.out.println();
        System.out.println(html2);
 
        // using String#concat()
        System.out.println("\n Multiline SQL/JSON/HTML before text blocks (using String#concat()):");
        String sql3 = "UPDATE \"public\".\"office\"\n"
                .concat("SET (\"address_first\", \"address_second\", \"phone\") =\n")
                .concat("  (SELECT \"public\".\"employee\".\"first_name\",\n")
                .concat("          \"public\".\"employee\".\"last_name\", ?\n")
                .concat("   FROM \"public\".\"employee\"\n")
                .concat("   WHERE \"public\".\"employee\".\"job_title\" = ?;");
 
        String json3 = "{\n"
                .concat("  \"widget\": {\n")
                .concat("    \"debug\": \"on\",\n")
                .concat("    \"window\": {\n")
                .concat("      \"title\": \"Sample Widget 1\",\n")
                .concat("      \"name\": \"back_window\"\n")
                .concat("    },\n")
                .concat("    \"image\": {\n")
                .concat("      \"src\": \"images\\sw.png\"\n")
                .concat("    },\n")
                .concat("    \"text\": {\n")
                .concat("      \"data\": \"Click Me\",\n")
                .concat("      \"size\": 39\n")
                .concat("    }\n")
                .concat("  }\n")
                .concat("}");
 
        String html3 = "
\n"
                .concat("  
\n")
                .concat("    
\n")
                .concat("    
\n")
                .concat("  
\n")
                .concat("  
\n")
                .concat("    
\n")
                .concat("    
\n")
                .concat("    
\n")
                .concat("  
\n")
                .concat("
Name
Age
John
Smith
22
");
 
        System.out.println(sql3);
        System.out.println();
        System.out.println(json3);
        System.out.println();
        System.out.println(html3);
 
        // 使用 string format连接
        System.out.println("\n Multiline SQL/JSON/HTML before text blocks (using String#format()):");
        String sql4 = String.format("%s%s%s%s%s%s",
                "UPDATE \"public\".\"office\"\n",
                "SET (\"address_first\", \"address_second\", \"phone\") =\n",
                "  (SELECT \"public\".\"employee\".\"first_name\",\n",
                "          \"public\".\"employee\".\"last_name\", ?\n",
                "   FROM \"public\".\"employee\"\n",
                "   WHERE \"public\".\"employee\".\"job_title\" = ?;");
 
        String json4 = String.format("%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s",
                "{\n",
                "  \"widget\": {\n",
                "    \"debug\": \"on\",\n",
                "    \"window\": {\n",
                "      \"title\": \"Sample Widget 1\",\n",
                "      \"name\": \"back_window\"\n",
                "    },\n",
                "    \"image\": {\n",
                "      \"src\": \"images\\sw.png\"\n",
                "    },\n",
                "    \"text\": {\n",
                "      \"data\": \"Click Me\",\n",
                "      \"size\": 39\n",
                "    }\n",
                "  }\n",
                "}");
 
        String html4 = String.format("%s%s%s%s%s%s%s%s%s%s%s",
                "
\n",
                "  
\n",
                "    
\n",
                "    
\n",
                "  
\n",
                "  
\n",
                "    
\n",
                "    
\n",
                "    
\n",
                "  
\n",
                "
Name
Age
John
Smith
22
");
 
        System.out.println(sql4);
        System.out.println();
        System.out.println(json4);
        System.out.println();
        System.out.println(html4);
 
        // jdk 8 s可以使用String ,join 进行字符串连接
        System.out.println("\n Multiline SQL/JSON/HTML before text blocks (using String#join()):");
        String sql5 = String.join("\n",
                "UPDATE \"public\".\"office\"",
                "SET (\"address_first\", \"address_second\", \"phone\") =",
                "  (SELECT \"public\".\"employee\".\"first_name\",",
                "          \"public\".\"employee\".\"last_name\", ?",
                "   FROM \"public\".\"employee\"",
                "   WHERE \"public\".\"employee\".\"job_title\" = ?;");
 
        String json5 = String.join("\n",
                "{",
                "  \"widget\": {",
                "    \"debug\": \"on\",",
                "    \"window\": {",
                "      \"title\": \"Sample Widget 1\",",
                "      \"name\": \"back_window\"",
                "    },",
                "    \"image\": {",
                "      \"src\": \"images\\sw.png\"",
                "    },",
                "    \"text\": {",
                "      \"data\": \"Click Me\",",
                "      \"size\": 39",
                "    }",
                "  }",
                "}");
 
        String html5 = String.join("\n",
                "
",
                "  
",
                "    
",
                "    
",
                "  
",
                "  
",
                "    
",
                "    
",
                "    
",
                "  
",
                "
Name
Age
John
Smith
22
");
 
        System.out.println(sql5);
        System.out.println();
        System.out.println(json5);
        System.out.println();
        System.out.println(html5);
 
        // 使用 StringJoiner
        System.out.println("\n Multiline SQL/JSON/HTML before text blocks (using StringJoiner):");
        StringJoiner sql6 = new StringJoiner("\n");
        sql6.add("UPDATE \"public\".\"office\"")
                .add("SET (\"address_first\", \"address_second\", \"phone\") =")
                .add("  (SELECT \"public\".\"employee\".\"first_name\",")
                .add("          \"public\".\"employee\".\"last_name\", ?")
                .add("   FROM \"public\".\"employee\"")
                .add("   WHERE \"public\".\"employee\".\"job_title\" = ?;");
 
        StringJoiner json6 = new StringJoiner("\n");
        json6.add("{")
                .add("  \"widget\": {")
                .add("    \"debug\": \"on\",")
                .add("    \"window\": {")
                .add("      \"title\": \"Sample Widget 1\",")
                .add("      \"name\": \"back_window\"")
                .add("    },")
                .add("    \"image\": {")
                .add("      \"src\": \"images\\sw.png\"")
                .add("    },")
                .add("    \"text\": {")
                .add("      \"data\": \"Click Me\",")
                .add("      \"size\": 39")
                .add("    }")
                .add("  }")
                .add("}");
 
        StringJoiner html6 = new StringJoiner("\n");
        html6.add("
")
                .add("  
")
                .add("    
")
                .add("    
")
                .add("  
")
                .add("  
")
                .add("    
")
                .add("    
")
                .add("    
")
                .add("  
")
                .add("
Name
Age
John
Smith
22
");
 
        System.out.println(sql6);
        System.out.println();
        System.out.println(json6);
        System.out.println();
        System.out.println(html6);
 
 
        //  using Collectors#joining()
        System.out.println("\n Multiline SQL/JSON/HTML before text blocks (using Collectors#joining()):");
        String sql7 = Stream.of(
                "UPDATE \"public\".\"office\"",
                "SET (\"address_first\", \"address_second\", \"phone\") =",
                "  (SELECT \"public\".\"employee\".\"first_name\",",
                "          \"public\".\"employee\".\"last_name\", ?",
                "   FROM \"public\".\"employee\"",
                "   WHERE \"public\".\"employee\".\"job_title\" = ?;")
                .collect(Collectors.joining(String.valueOf("\n")));
 
        String json7 = Stream.of(
                "{",
                "  \"widget\": {",
                "    \"debug\": \"on\",",
                "    \"window\": {",
                "      \"title\": \"Sample Widget 1\",",
                "      \"name\": \"back_window\"",
                "    },",
                "    \"image\": {",
                "      \"src\": \"images\\sw.png\"",
                "    },",
                "    \"text\": {",
                "      \"data\": \"Click Me\",",
                "      \"size\": 39",
                "    }",
                "  }",
                "}")
                .collect(Collectors.joining(String.valueOf("\n")));
 
        String html7 = Stream.of(
                "
",
                "  
",
                "    
",
                "    
",
                "  
",
                "  
",
                "    
",
                "    
",
                "    
",
                "  
",
                "
Name
Age
John
Smith
22
")
                .collect(Collectors.joining(String.valueOf("\n")));
 
        System.out.println(sql7);
        System.out.println();
        System.out.println(json7);
        System.out.println();
        System.out.println(html7);
 
        // Starting with JDK 13/15
        // using text blocks
        System.out.println("\n Multiline SQL/JSON/HTML using text blocks:");
        String sql8 = """
                      UPDATE "public"."office"
                      SET ("address_first", "address_second", "phone") =
                        (SELECT "public"."employee"."first_name",
                                "public"."employee"."last_name", ?
                         FROM "public"."employee"
                         WHERE "public"."employee"."job_title" = ?""";
 
        String json8 = """
                       {
                         "widget": {
                           "debug": "on",
                           "window": {
                             "title": "Sample Widget 1",
                             "name": "back_window"
                           },
                           "image": {
                             "src": "images\\sw.png"
                           },
                           "text": {
                             "data": "Click Me",
                             "size": 39
                           }
                         }
                       }""";
 
        String html8 = """
                       
                         
                           
                           
                         
                         
                           
                           
                           
                         
                       
Name
Age
John
Smith
22
""";
 
        System.out.println(sql8);
        System.out.println();
        System.out.println(json8);
        System.out.println();
        System.out.println(html8);
 
 
    }
}
2、举例说明文本块分隔符的用法
这个语法跟python的类似
public class Main {
 
    public static void main(String[] args) {
 
        System.out.println("The common usage of text block delimiters:\n");
        String sql1 = """
                      UPDATE "public"."office"
                      SET ("address_first", "address_second", "phone") =
                        (SELECT "public"."employee"."first_name",
                                "public"."employee"."last_name", ?
                         FROM "public"."employee"
                         WHERE "public"."employee"."job_title" = ?""";
 
        System.out.println("-- BEFORE TEXT BLOCK --");
        System.out.println(sql1);
        System.out.println("-- AFTER TEXT BLOCK --");
        
        System.out.println("\nKeep the opening delimiter and the content on the "
                + "same line is not accepted (does not compile)\n");
        /* 
        String not_compile = """UPDATE "public"."office"
                      SET ("address_first", "address_second", "phone") =
                        (SELECT "public"."employee"."first_name",
                                "public"."employee"."last_name", ?
                         FROM "public"."employee"
                         WHERE "public"."employee"."job_title" = ?""";
        */
 
        System.out.println("\nShift-left the content has no effect:\n");
        String sql2 = """
          UPDATE "public"."office"
          SET ("address_first", "address_second", "phone") =
            (SELECT "public"."employee"."first_name",
                    "public"."employee"."last_name", ?
             FROM "public"."employee"
             WHERE "public"."employee"."job_title" = ?""";
        
        System.out.println("-- BEFORE TEXT BLOCK --");
        System.out.println(sql2);
        System.out.println("-- AFTER TEXT BLOCK --");        
        
        System.out.println("\nShift-right the opening/closing delimiter has no effect:\n");
        String sql3 =                                           """
          UPDATE "public"."office"
          SET ("address_first", "address_second", "phone") =
            (SELECT "public"."employee"."first_name",
                    "public"."employee"."last_name", ?
             FROM "public"."employee"
             WHERE "public"."employee"."job_title" = ?          """;
        
        System.out.println("-- BEFORE TEXT BLOCK --");
        System.out.println(sql3);
        System.out.println("-- AFTER TEXT BLOCK --");
                
        System.out.println("\nMoving the closing delimiter on its own line (1):\n");
        String sql4 = """                      
                      UPDATE "public"."office"
                      SET ("address_first", "address_second", "phone") =
                        (SELECT "public"."employee"."first_name",
                                "public"."employee"."last_name", ?
                         FROM "public"."employee"
                         WHERE "public"."employee"."job_title" = ?
                      """;
 
        System.out.println("-- BEFORE TEXT BLOCK --");
        System.out.println(sql4);
        System.out.println("-- AFTER TEXT BLOCK --");
        
        System.out.println("\nMoving the closing delimiter on its own line (2):\n");
        String sql5 = """                      
          UPDATE "public"."office"
          SET ("address_first", "address_second", "phone") =
            (SELECT "public"."employee"."first_name",
                    "public"."employee"."last_name", ?
             FROM "public"."employee"
             WHERE "public"."employee"."job_title" = ?
          """;
 
        System.out.println("-- BEFORE TEXT BLOCK --");
        System.out.println(sql5);
        System.out.println("-- AFTER TEXT BLOCK --");
        
        System.out.println("\nMoving on its own line and shift-left the closing delimiter:\n");
        String sql6 = """                      
                      UPDATE "public"."office"
                      SET ("address_first", "address_second", "phone") =
                        (SELECT "public"."employee"."first_name",
                                "public"."employee"."last_name", ?
                         FROM "public"."employee"
                         WHERE "public"."employee"."job_title" = ?
        """;
 
        System.out.println("-- BEFORE TEXT BLOCK --");
        System.out.println(sql6);
        System.out.println("-- AFTER TEXT BLOCK --");
        
        System.out.println("\nMoving on its own line and shift-right the closing delimiter:\n");
        String sql7 = """                      
                      UPDATE "public"."office"
                      SET ("address_first", "address_second", "phone") =
                        (SELECT "public"."employee"."first_name",
                                "public"."employee"."last_name", ?
                         FROM "public"."employee"
                         WHERE "public"."employee"."job_title" = ?
                                          """;
 
        System.out.println("-- BEFORE TEXT BLOCK --");
        System.out.println(sql7);
        System.out.println("-- AFTER TEXT BLOCK --");
    }
}


                    相关阅读:

                    
外包干了一个月，技术明显进步。。。。。                            

SciChart WPF Charts SDK v6.x                            

设计模式 14 模板模式                            

kubernetes集群搭建                            

期货怎么克服频繁止损（期货交易怎么止损）                            

Docker安装canal、mysql进行简单测试与实现redis和mysql缓存一致性                            

美团2017年CodeM大赛-资格赛 NC13224 送外卖（记忆化搜索 or 预处理 dfs）                            

文件包含漏洞详解                            

[AI]Python中的Restful                            

【解决方法】错误：无法和SFTP服务器建立FTP连接，请选择合适的协议                            

                    
                

                    原文地址：https://blog.csdn.net/wangjunji34478/article/details/133392469
                

            

                

                    最新文章
                
                

                    
沪漂五周年了：我越来越迷茫了                            

Agentic Skill Routing 实战：别再把所有 Skill 塞进 AI Agent 上下文                            

MySQL-Seconds_behind_master的精度误差                            

[MAF预定义ChatClient中间件-03]CachingChatClient——利用缓存省钱省时间                            

AI的至暗历史：从万众期待到被政府撤资，AI的两次死亡徘徊                            

Agent OS ：五种驯服不确定性的范式                            

PortSwigger SQL注入LAB11                            

数据库即时编译JIT                            

[Begin]AI Learn Data Day 0                            

深度学习进阶（二十七）现代 LLM 的核心架构设计其二：SwiGLU                            

                    
                
            

            

                

                    热门文章
                
                

                    
十款代码表白小特效 一个比一个浪漫 赶紧收藏起来吧！！！                            

奉劝各位学弟学妹们，该打造你的技术影响力了！                            

五年了，我在 CSDN 的两个一百万。                            

Java俄罗斯方块，老程序员花了一个周末，连接中学年代！                            

面试官都震惊，你这网络基础可以啊！                            

你真的会用百度吗？我不信 — 那些不为人知的搜索引擎语法                            

心情不好的时候，用 Python 画棵樱花树送给自己吧                            

通宵一晚做出来的一款类似CS的第一人称射击游戏Demo！原来做游戏也不是很难，连憨憨学妹都学会了！                            

13 万字 C 语言从入门到精通保姆级教程2021 年版                            

10行代码集2000张美女图，Python爬虫120例，再上征途