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java中如何从键盘读入一个数
可以通过”Scanner“函数 直接输入参数的形式,来实现输入语句,举例:
import java.util.Scanner;
public class Test {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
System.out.println("请输入一个整数:");
int length=input.nextInt();//输入一个整数
System.out.println("输入的整数是:"+length);}
}
备注:Scanner函数就是用来进行语句输入的,上面举例的是整数类型,也可以用以下语句“String length=input.next()”,输入的就是字符串类型等。
如何在java中读入整数
import java.util.Scanner;
public class Demo {
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("请输入一个整数");
int x = scan.nextInt();
System.out.println("输入的证书是:"+x);
}
java中读入和输出文本文件
写文件
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
public class WriteFile {
public static void main(String[] args) {
File file = new File("F:" + File.separator + "abcd.txt");
try {
// 注意,这个地方,那个true的参数,代表如果这个文件已经存在了,就把新的内容添加到该文件的最后
// 如果你想重新创建新文件,把true改成false就好了
Writer writer = new OutputStreamWriter(new FileOutputStream(file, true), "GBK");
StringBuilder builder = new StringBuilder();
for (int i = 0; i 100; i++) {
int temp = (int) ((Math.random() + 1) * 1000);
builder.append(String.valueOf(temp));
builder.append("|");
temp = (int) ((Math.random() + 1) * 1000);
builder.append(String.valueOf(temp)).append("\n");
}
writer.write(builder.toString());
writer.close();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
读文件
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
public class ReadFile {
public static void main(String[] args) {
File file = new File("F:" + File.separator + "abcd.txt");
String s = "";
try {
InputStreamReader read = new InputStreamReader(new FileInputStream(file), "GBK");
BufferedReader reader = new BufferedReader(read);
String line;
while ((line = reader.readLine()) != null) {
s += line + "\n";
}
reader.close();
read.close();
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(s);
}
}数据的格式: