【Java基础】输入与输出

素颜马尾好姑娘i 2024-03-26 11:13 98阅读 0赞

## 输入与输出 ##

### 输入 ###

获取用键盘输入常用的两种方法

方法 1：通过 `Scanner`

Scanner input = new Scanner(System.in);
    String s  = input.nextLine();
    input.close();

方法 2：通过 `BufferedReader`

BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
    String s = input.readLine();

### 输出 ###

System.out.println("字符串");//换行打印
    System.out.print("\n");//换行打印
    System.out.print("字符串");//换行打印
    System.out.print(a);//不换行打印变量
    System.out.print("字符串"+a);//混合输出字符串和变量值
    System.out.printf("%");//按格式输出

[printf 格式化输出符号详细说明\_xiexievv的专栏-CSDN博客\_printf格式化输出][printf _xiexievv_-CSDN_printf]

### 格式化输入与输出 ###

<table> 
 <thead> 
  <tr> 
   <th>Converter</th> 
   <th>Flag</th> 
   <th>Explanation</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>d</td> 
   <td></td> 
   <td>A decimal integer.</td> 
  </tr> 
  <tr> 
   <td>f</td> 
   <td></td> 
   <td>A float.</td> 
  </tr> 
  <tr> 
   <td>n</td> 
   <td></td> 
   <td>A new line character appropriate to the platform running the application. You should always use <code>%n</code>, rather than <code>\n</code>.</td> 
  </tr> 
  <tr> 
   <td>tB</td> 
   <td></td> 
   <td>A date &amp; time conversion—locale-specific full name of month.</td> 
  </tr> 
  <tr> 
   <td>td, te</td> 
   <td></td> 
   <td>A date &amp; time conversion—2-digit day of month. td has leading zeroes as needed, te does not.</td> 
  </tr> 
  <tr> 
   <td>ty, tY</td> 
   <td></td> 
   <td>A date &amp; time conversion—ty = 2-digit year, tY = 4-digit year.</td> 
  </tr> 
  <tr> 
   <td>tl</td> 
   <td></td> 
   <td>A date &amp; time conversion—hour in 12-hour clock.</td> 
  </tr> 
  <tr> 
   <td>tM</td> 
   <td></td> 
   <td>A date &amp; time conversion—minutes in 2 digits, with leading zeroes as necessary.</td> 
  </tr> 
  <tr> 
   <td>tp</td> 
   <td></td> 
   <td>A date &amp; time conversion—locale-specific am/pm (lower case).</td> 
  </tr> 
  <tr> 
   <td>tm</td> 
   <td></td> 
   <td>A date &amp; time conversion—months in 2 digits, with leading zeroes as necessary.</td> 
  </tr> 
  <tr> 
   <td>tD</td> 
   <td></td> 
   <td>A date &amp; time conversion—date as %tm%td%ty</td> 
  </tr> 
  <tr> 
   <td></td> 
   <td>08</td> 
   <td>Eight characters in width, with leading zeroes as necessary.</td> 
  </tr> 
  <tr> 
   <td></td> 
   <td>+</td> 
   <td>Includes sign, whether positive or negative.</td> 
  </tr> 
  <tr> 
   <td></td> 
   <td>,</td> 
   <td>Includes locale-specific grouping characters.</td> 
  </tr> 
  <tr> 
   <td></td> 
   <td>-</td> 
   <td>Left-justified…</td> 
  </tr> 
  <tr> 
   <td></td> 
   <td>.3</td> 
   <td>Three places after decimal point.</td> 
  </tr> 
  <tr> 
   <td></td> 
   <td>10.3</td> 
   <td>Ten characters in width, right justified, with three places after decimal point.</td> 
  </tr> 
 </tbody> 
</table>

![在这里插入图片描述][5dd0312da963490fbc846a62c35a50a7.png]

float a=0.23456f;
            System.out.format("a保留3位小数：%.3f",a);//a保留3位小数：0.235

##### DecimalFormat #####

[printf _xiexievv_-CSDN_printf]: https://blog.csdn.net/xiexievv/article/details/6831194?utm_medium=distribute.pc_relevant.none-task-blog-2~default~BlogCommendFromBaidu~default-16.no_search_link&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2~default~BlogCommendFromBaidu~default-16.no_search_link
[5dd0312da963490fbc846a62c35a50a7.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/e895686a5f0e4c758400508095f8c598.png