ACM之Java输入输出

Myth丶恋晨 2022-07-16 07:52 189阅读 0赞

**转自： [http://blog.csdn.net/shijiebei2009/article/details/17305223][http_blog.csdn.net_shijiebei2009_article_details_17305223]**

**一、Java之ACM注意点**

1. 类名称必须采用public class Main方式命名

2. 在有些OJ系统上，即便是输出的末尾多了一个“ ”，程序可能会输出错误，所以在我看来好多OJ系统做的是非常之垃圾

3. 有些OJ上的题目会直接将OI上的题目拷贝过来，所以即便是题目中有输入和输出文件，可能也不需要，因为在OJ系统中一般是采用标准输入输出，不需要文件

4. 在有多行数据输入的情况下，一般这样处理，

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1.  **static** Scanner in = **new** Scanner(System.in); 
2.  **while**(in.hasNextInt()) 
3.  或者是 
4.  **while**(in.hasNext())

5. 有关System.nanoTime() 函数的使用，该函数用来 返回最准确的可用系统计时器的当前值，以毫微秒为单位。

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1.  **long** startTime = System.nanoTime(); 
2.  // ... the code being measured ...
3.  **long** estimatedTime = System.nanoTime() - startTime;

## 二、Java之输入输出处理 ##

由于ACM竞赛题目的输入数据和输出数据一般有多组（不定），并且格式多种多样，所以，如何处理题目的输入输出是对大家的一项最基本的要求。这也是困扰初学者的一大问题。

1. 输入：

格式1：Scanner sc = new Scanner (new BufferedInputStream(System.in));

格式2：Scanner sc = new Scanner (System.in);

在读入数据量大的情况下，格式1的速度会快些。

读一个整数： int n = sc.nextInt(); 相当于 scanf("%d", &n); 或 cin >> n;

读一个字符串：String s = sc.next(); 相当于 scanf("%s", s); 或 cin >> s;

读一个浮点数：double t = sc.nextDouble(); 相当于 scanf("%lf", &t); 或 cin >> t;

读一整行： String s = sc.nextLine(); 相当于 gets(s); 或 cin.getline(...);

判断是否有下一个输入可以用sc.hasNext()或sc.hasNextInt()或sc.hasNextDouble()或sc.hasNextLine()

例1：读入整数

例2：读入实数

输入数据有多组，每组占2行，第一行为一个整数N，指示第二行包含N个实数。

例3：读入字符串【杭电2017 字符串统计】

输入数据有多行，第一行是一个整数n，表示测试实例的个数，后面跟着n行，每行包括一个由字母和数字组成的字符串。

例3：读入字符串【杭电2005 第几天？】

2. 输出

函数：

System.out.print();

System.out.println();

System.out.format();

System.out.printf();

例4 杭电1170Balloon Comes!

Give you an operator (+,-,\*, / --denoting addition, subtraction, multiplication, division respectively) and two positive integers, your task is to output the result.

Input

Input contains multiple test cases. The first line of the input is a single integer T (0<T<1000) which is the number of test cases. T test cases follow. Each test case contains a char C (+,-,\*, /) and two integers A and B(0<A,B<10000).Of course, we all know that A and B are operands and C is an operator.

Output

For each case, print the operation result. The result should be rounded to 2 decimal places If and only if it is not an integer.

Sample Input

\+ 1 2

\- 1 2

\* 1 2

/ 1 2

Sample Output

\-1

0.50

3. 规格化的输出：  
函数：  
// 这里0指一位数字，\#指除0以外的数字(如果是0，则不显示),四舍五入.  
DecimalFormat fd = new DecimalFormat("\#.00\#");  
DecimalFormat gd = new DecimalFormat("0.000");  
System.out.println("x =" + fd.format(x));  
System.out.println("x =" + gd.format(x));

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 <ol style="padding:0px; border:none; list-style-position:initial; background-color:rgb(255,255,255); color:rgb(92,92,92); margin:0px 0px 1px 45px!important"> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> public&nbsp;static&nbsp;void&nbsp;main(String[]&nbsp;args)&nbsp;{&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;NumberFormat&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"000000");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;String&nbsp;&nbsp;s&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-001235&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"##");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-1235&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(0);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"##00");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(0);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;00&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;".00");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-.57&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"0.00");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-0.57&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"#.#");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-1234.6&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"#.######");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-1234.567&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;".######");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-1234.567&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"#.000000");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-1234.567000&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"#,###,###");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-1,235&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234567.890);&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-1,234,568&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;The&nbsp;&nbsp;&nbsp;;&nbsp;&nbsp;&nbsp;symbol&nbsp;&nbsp;&nbsp;is&nbsp;&nbsp;&nbsp;used&nbsp;&nbsp;&nbsp;to&nbsp;&nbsp;&nbsp;specify&nbsp;&nbsp;&nbsp;an&nbsp;&nbsp;&nbsp;alternate&nbsp;&nbsp;&nbsp;pattern&nbsp;&nbsp;&nbsp;for&nbsp;&nbsp;&nbsp;negative&nbsp;&nbsp;&nbsp;values&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"#;(#)&nbsp;");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;(1235)&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;The&nbsp;&nbsp;&nbsp;'&nbsp;&nbsp;&nbsp;symbol&nbsp;&nbsp;&nbsp;is&nbsp;&nbsp;&nbsp;used&nbsp;&nbsp;&nbsp;to&nbsp;&nbsp;&nbsp;quote&nbsp;&nbsp;&nbsp;literal&nbsp;&nbsp;&nbsp;symbols&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"&nbsp;'#&nbsp;'#&nbsp;");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;&nbsp;&nbsp;-#1235&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"&nbsp;'abc&nbsp;'#&nbsp;");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-1234.567);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;-&nbsp;abc&nbsp;1235&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> formatter&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;new&nbsp;&nbsp;&nbsp;DecimalFormat(&nbsp;"#.##%");&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;s&nbsp;&nbsp;&nbsp;=&nbsp;&nbsp;&nbsp;formatter.format(-12.5678987);&nbsp;&nbsp;&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; background-color:rgb(248,248,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(s);&nbsp;&nbsp;</li> 
 <li style="border-style:none none none solid; border-left-width:3px; border-left-color:rgb(108,226,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> }&nbsp;&nbsp;</li> 
 </ol> 
 </div> </td> 
 </tr> 
 </tbody> 
</table>

4. 字符串处理 String

String 类用来存储字符串，可以用charAt方法来取出其中某一字节，计数从0开始：

String a = "Hello"; // a.charAt(1) = 'e'

用substring方法可得到子串，如上例

System.out.println(a.substring(0, 4)) // output "Hell"

注意第2个参数位置上的字符不包括进来。这样做使得 s.substring(a, b) 总是有 b-a个字符。

字符串连接可以直接用 \+ 号，如

String a = "Hello";

String b = "world";

System.out.println(a + ", " + b + "!"); // output "Hello, world!"

如想直接将字符串中的某字节改变，可以使用另外的StringBuffer类。

5. 高精度  
BigInteger和BigDecimal可以说是acmer选择java的首要原因。  
函数：add, subtract, divide, mod, compareTo等，其中加减乘除模都要求是BigInteger(BigDecimal)和BigInteger(BigDecimal)之间的运算，所以需要把int(double)类型转换为BigInteger(BigDecimal)，用函数BigInteger.valueOf().

6. 进制转换 
String st = Integer.toString(num, base); // 把num当做10进制的数转成base进制的st(base <= 35). 
int num = Integer.parseInt(st, base); // 把st当做base进制，转成10进制的int(parseInt有两个参数,第一个为要转的字符串,第二个为说明是什么进制). 
BigInter m = new BigInteger(st, base); // st是字符串，base是st的进制. 
7. 数组排序 
函数：Arrays.sort();

[http_blog.csdn.net_shijiebei2009_article_details_17305223]: http://blog.csdn.net/shijiebei2009/article/details/17305223
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