Java利用for循环打印菱形的实例教程

Java for循环打印菱形

Java代码输出菱形的方法和思路有很多，在此分享一个稍带模块化拆分思想的解决方案，将需要输出的菱形拆分成8个模块（如下图），每个模块独立实现输出。

优点：8个模块之间耦合性降低，灵活性增强。也就是说我们可以独立的控制这8个模块中任意一个模块的输出内容来灵活应对业务逻辑的变更。

按照上图标好的顺序依次实现这8个模块的代码，当1458模块输出为空格时，其中2367模块的组合，就是一个菱形。

思路分析：

1      ######*######  第一排 模块1[6个"#"]+模块2[1个"*"]+模块3[0个"*"]+模块4[6个"#"]
        2      #####***#####
        3      ####*****####
        4      ###*******###
        5      ##*********##
        6      #***********#
    --------------------------------------------------------
        7      ##*********##  第七排 模块5[2个"#"]+模块6[5个"*"]+模块7[4个"*"]+模块8[2个"#"]
        8      ###*******###
        9      ####*****####
       10      #####***#####
       11      ######*######

代码示例：

public class Demo {

 public static void main(String[] args) {

 //为了输出效果在输出时将思路分析中的"#"替换为" "空格输出

 for (int i = 1; i <= 11; i++) {

 if (i <= 6) {
 //当i <=6时打印上三角形
 //模块 1
 for (int j = 6; j >= i; j--) {
  System.out.print(" ");
 }
 //模块 2
 for (int j = 0; j < i; j++) {
  System.out.print("*");
 }
 //模块 3[同一排中模块3的"*"个数总比模块2少1个，所以这里j <i-1作为循环条件即可]
 for (int j = 0; j < i - 1; j++) {
  System.out.print("*");
 }
 //模块 4
 for (int j = 6; j >= i; j--) {
  System.out.print(" ");
 }
 //换行
 System.out.println();
 } else {
 //当i >6时打印下三角形
 //模块 5
 for (int j = 7; j <= i + 1; j++) {
  System.out.print(" ");
 }
 //模块 6
 for (int j = 11; j >= i; j--) {
  System.out.print("*");
 }
 //模块 7
 for (int j = 11; j >= i + 1; j--) {
  System.out.print("*");
 }
 //模块 8
 for (int j = 7; j <= i + 1; j++) {
  System.out.print(" ");
 }

 //换行
 System.out.println();
 }
 }
 }
}

运行结果：

F:\software\Java\jdk1.8.0_121\bin\java.exe "-javaagent:D:\IntelliJ IDEA 2019.1.4\lib\idea_rt.jar=50753:D:\IntelliJ IDEA 2019.1.4\bin" -Dfile.encoding=UTF-8 -classpath F:\software\Java\jdk1.8.0_121\jre\lib\charsets.jar;F:\software\Java\jdk1.8.0_121\jre\lib\deploy.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\access-bridge-64.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\cldrdata.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\dnsns.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\jaccess.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\jfxrt.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\localedata.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\nashorn.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\sunec.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\sunjce_provider.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\sunmscapi.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\sunpkcs11.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\zipfs.jar;F:\software\Java\jdk1.8.0_121\jre\lib\javaws.jar;F:\software\Java\jdk1.8.0_121\jre\lib\jce.jar;F:\software\Java\jdk1.8.0_121\jre\lib\jfr.jar;F:\software\Java\jdk1.8.0_121\jre\lib\jfxswt.jar;F:\software\Java\jdk1.8.0_121\jre\lib\jsse.jar;F:\software\Java\jdk1.8.0_121\jre\lib\management-agent.jar;F:\software\Java\jdk1.8.0_121\jre\lib\plugin.jar;F:\software\Java\jdk1.8.0_121\jre\lib\resources.jar;F:\software\Java\jdk1.8.0_121\jre\lib\rt.jar;D:\ideastudyspace\spring_study\spring-study\spring-study-aop\target\classes;E:\software\MavenRepository\org\aspectj\aspectjweaver\1.9.4\aspectjweaver-1.9.4.jar;E:\software\MavenRepository\org\springframework\spring-webmvc\5.2.0.RELEASE\spring-webmvc-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-aop\5.2.0.RELEASE\spring-aop-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-beans\5.2.0.RELEASE\spring-beans-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-context\5.2.0.RELEASE\spring-context-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-core\5.2.0.RELEASE\spring-core-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-jcl\5.2.0.RELEASE\spring-jcl-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-expression\5.2.0.RELEASE\spring-expression-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-web\5.2.0.RELEASE\spring-web-5.2.0.RELEASE.jar;E:\software\MavenRepository\com\alibaba\fastjson\1.2.47\fastjson-1.2.47.jar com.shiguang.test.Demo
      *     
     ***    
    *****   
   *******  
  ********* 
 ***********
  ********* 
   *******  
    *****   
     ***    
      *

Process finished with exit code 0

业务变更： 打印一个空心菱形

此时只需要将1458模块输出为"*"，2367模块输出为空格即可得到一个空心菱形。

代码示例：

public class Demo2 {

 public static void main(String[] args) {

 for (int i = 1; i <= 11; i++) {

  if (i <= 6) {
  //当i <=6时打印上三角形
  //模块 1
  for (int j = 6; j >= i; j--) {
   System.out.print("*");
  }
  //模块 2
  for (int j = 0; j < i; j++) {
   System.out.print(" ");
  }
  //模块 3[同一排中模块3的"*"个数总比模块2少1个，所以这里j <i-1作为循环条件即可]
  for (int j = 0; j < i - 1; j++) {
   System.out.print(" ");
  }
  //模块 4
  for (int j = 6; j >= i; j--) {
   System.out.print("*");
  }
  //换行
  System.out.println();
  } else {
  //当i >6时打印下三角形
  //模块 5
  for (int j = 7; j <= i + 1; j++) {
   System.out.print("*");
  }
  //模块 6
  for (int j = 11; j >= i; j--) {
   System.out.print(" ");
  }
  //模块 7
  for (int j = 11; j >= i + 1; j--) {
   System.out.print(" ");
  }
  //模块 8
  for (int j = 7; j <= i + 1; j++) {
   System.out.print("*");
  }

  //换行
  System.out.println();
  }
 }
 }
}

运行结果：

F:\software\Java\jdk1.8.0_121\bin\java.exe "-javaagent:D:\IntelliJ IDEA 2019.1.4\lib\idea_rt.jar=50681:D:\IntelliJ IDEA 2019.1.4\bin" -Dfile.encoding=UTF-8 -classpath F:\software\Java\jdk1.8.0_121\jre\lib\charsets.jar;F:\software\Java\jdk1.8.0_121\jre\lib\deploy.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\access-bridge-64.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\cldrdata.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\dnsns.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\jaccess.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\jfxrt.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\localedata.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\nashorn.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\sunec.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\sunjce_provider.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\sunmscapi.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\sunpkcs11.jar;F:\software\Java\jdk1.8.0_121\jre\lib\ext\zipfs.jar;F:\software\Java\jdk1.8.0_121\jre\lib\javaws.jar;F:\software\Java\jdk1.8.0_121\jre\lib\jce.jar;F:\software\Java\jdk1.8.0_121\jre\lib\jfr.jar;F:\software\Java\jdk1.8.0_121\jre\lib\jfxswt.jar;F:\software\Java\jdk1.8.0_121\jre\lib\jsse.jar;F:\software\Java\jdk1.8.0_121\jre\lib\management-agent.jar;F:\software\Java\jdk1.8.0_121\jre\lib\plugin.jar;F:\software\Java\jdk1.8.0_121\jre\lib\resources.jar;F:\software\Java\jdk1.8.0_121\jre\lib\rt.jar;D:\ideastudyspace\spring_study\spring-study\spring-study-aop\target\classes;E:\software\MavenRepository\org\aspectj\aspectjweaver\1.9.4\aspectjweaver-1.9.4.jar;E:\software\MavenRepository\org\springframework\spring-webmvc\5.2.0.RELEASE\spring-webmvc-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-aop\5.2.0.RELEASE\spring-aop-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-beans\5.2.0.RELEASE\spring-beans-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-context\5.2.0.RELEASE\spring-context-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-core\5.2.0.RELEASE\spring-core-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-jcl\5.2.0.RELEASE\spring-jcl-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-expression\5.2.0.RELEASE\spring-expression-5.2.0.RELEASE.jar;E:\software\MavenRepository\org\springframework\spring-web\5.2.0.RELEASE\spring-web-5.2.0.RELEASE.jar;E:\software\MavenRepository\com\alibaba\fastjson\1.2.47\fastjson-1.2.47.jar com.shiguang.test.Demo
****** ******
*****   *****
****     ****
***       ***
**         **
*           *
**         **
***       ***
****     ****
*****   *****
****** ******

Process finished with exit code 0

总结

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