java 输入一个数字符字符串

￡神魔★判官ぃ 2022-06-05 23:52 173阅读 0赞

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 <tbody style="margin:0px; padding:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:inherit; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline"> 
  <tr style="margin:0px; padding:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:inherit; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline"> 
   <td style="margin:0px; padding:5px; border:0px none; font-style:inherit; font-variant:inherit; font-weight:inherit; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline; max-width:780px"> 
    <div style="margin:0px; padding:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:inherit; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline; width:656px; height:0px"> 
    </div> <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:inherit; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline"> java不像C中拥有scanf这样功能强大的函数，大多是通过定义输入输出流对象。<br> 常用的类有BufferedReader，Scanner。<br> 实例程序：</p> <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:inherit; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline"> </p> <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> <span style="margin:0px; padding:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:700; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline">一，利用 Scanner 实现从键盘读入float &nbsp;</span><span style="font-family:inherit; font-size:undefined; font-style:inherit; font-weight:bold">integer &nbsp;string</span><span style="font-family:inherit; font-size:undefined; font-style:inherit; font-weight:700">型数据</span></p> 
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        Java代码 
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       <pre><code>导入java。util包中的scaner类
import java.util.*;
class Example
{
	public static void main(String args[])
	{
		Scanner in=new Scanner(System.in);//使用scanner类定义对象
		System.out.println("please input a float number");
		float a=in.nextFloat();//接受float型数据
		System.out.println(a);
		System.out.println("please input a integer number");
		int b=in.nextInt();//接收整形数据
		System.out.println(b);
		System.out.println("please input a string 没有空格");
		String c=in.next();//接收String型数据
		System.out.println(c);
	}
}</code></pre> 
       <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> <span style="margin:0px; padding:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:700; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline">&nbsp;二，利用 BufferedReader实现从键盘读入字符串并写进文件abc.txt中</span></p> 
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           Java代码 
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          <pre><code>import java.io.*;  
public class Test  
{  
    public static void main(String[] args) throws IOException  
    {  
        BufferedReader buf = new BufferedReader (new InputStreamReader(System.in));  
        BufferedWriter buff = new BufferedWriter(new FileWriter("abc.txt"));  
        String str = buf.readLine();  
        while(!str.equals("exit"))  
        {  
            buff.write(str);  
            buff.newLine();  
            str = buf.readLine();  
        }  
        buf.close();  
        buff.close();  
    }  
}  </code></pre> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> 关于JDK1.5 Scanner类的说明</p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> Scanner是SDK1.5新增的一个类,可是使用该类创建一个对象.<br> Scanner reader=new Scanner(System.in);</p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> 然后reader对象调用下列方法(函数),读取用户在命令行输入的各种数据类型:<br> next.Byte(),nextDouble(),nextFloat,nextInt(),nextLine(),nextLong(),nextShot()</p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> <br> 使用nextLine()方法输入行中可能包含空格.如果读取的是一个单词,则可调用<br> .next()方法</p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> &nbsp;</p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> <span style="margin:0px; padding:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:700; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline">三、Scanner和BufferedReader的区别</span></p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> <span style="margin:0px; padding:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:700; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline"><br> </span>在命令行模式下要输入数据至程序中时,我们可以使用标准输入串对象System.in.但是,我们并不经常直接使用它,因为System.in提供的 read方法每次只能读取一个字节的数据,而我们平时所应用的通常是读取一个字符串或者是一个数字,所以read方法所以提供的功能,对我们来说并没有太大的用处.<br> 在Java SE 6中,可以使用Scanner类取得用户的输入,Scanner类位于java.util包中,如果你要使用Scanner取得用户输入的话,要加上 import java.util.Scanner;这条语句.import的功能是告诉编译器,你将使用java.util包中的Scanner类.<br> 我们来看一个例子:</p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> </p> 
          <pre><code>import java.util.Scanner;  
public class Test  
{  
    public static void main(String[] args)  
    {  
        Scanner scan = new Scanner(System.in);  
        System.out.println("请输入一个字符串:");  
        System.out.println("您输入的字符串是:" + scan.next());  
    }  
} </code></pre> 
          <p></p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> 运行上面的程序,你将会看到你输入的字符串将在下面原样显示出来.<br> 我们来看看这个程序中每条语句的意思:<br> new是创建一个对象,程序中new的意思是创建了一个Scanner类的对象scan.但是在创建Scanner类的对象时,需要用System.in 作为它的参数,也可以将Scanner看作是System.in对象的支持者,System.in取得用户输入的内容后,交给Scanner来作一些处理.<br> Scanner类中提供了多个方法:<br> next():取得一个字符串;<br> nextInt():将取得的字符串转换成int类型的整数;<br> nextFloat():将取得的字符串转换成float型;<br> nextBoolean():将取得的字符串转换成boolean型;</p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> 用Scanner获得用户的输入非常的方便,但是Scanner取得输入的依据是空格符,包括空格键,Tab键和Enter键.当按下这其中的任一键时,Scanner就会返回下一个输入. 当你输入的内容中间包括空格时,显然,使用Scanner就不能完整的获得你输入的字符串.这时候我们可以考虑使用BufferedReader类取得输入.其实在Java SE 1.4及以前的版本中,尚没有提供Scanner方法,我们获得输入时也是使用BufferReader的.<br> BufferedReader类位于java.io包中,所以要使用这个类,就要引入java.io这个包:import java.io.BufferedReader.<br> 使用BufferedReader对象的readLine()方法必须处理java.io.IOException异常(Exception).<br> 使用BufferedReader来取得输入,理解起来要复杂得多.但是使用这个方法是固定的,每次使用前先如法炮制就可以了.</p> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));<br> String text = buffer.readLine();<br> readLine()方法会返回用户在按下Enter键之前的所有字符输入,不包括最后按下的Enter返回字符.<br> 完整的示例程序如下:</p> 
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              Java代码 
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          <pre><code>import java.io.BufferedReader;  
import java.io.IOException;  
import java.io.InputStreamReader;  
public class TestBufferedReader  
{  
    public static void main(String[] args) throws IOException  
    {  
        BufferedReader buffer = new BufferedReader(new InputStreamReader(System.in));  
        System.out.println("请输入一串字符串");  
        String text = buffer.readLine();  
        System.out.println("您输入的字符串是:" + text);  
    }  
}  </code></pre> 
          <br> 
          <p style="margin-top:0px; margin-bottom:0px; padding-top:0px; padding-bottom:0px; border:0px; font-size:16px; line-height:inherit; font-family:Arial,Helvetica,&quot;Hiragino Sans GB&quot;,&quot;Microsoft YaHei&quot;,sans-serif; vertical-align:baseline; color:rgb(68,68,68)"> <span style="margin:0px; padding:0px; border:0px; font-style:inherit; font-variant:inherit; font-weight:700; font-size:undefined; line-height:inherit; font-family:inherit; vertical-align:baseline">四，利用 System.in.read 实现从键盘读入char 型数据</span></p> 
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              Java代码&nbsp; 
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             <pre><code>import java.io.IOException;
class Example
{
	public static void main(String args[])throws IOException  
	{
		System.out.println("please input a char");  
        char c=(char)System.in.read();  
        System.out.println(c);  
	}
}</code></pre> 
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