import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
 
public class test {
    public static String txt2String(File file){
        StringBuilder result = new StringBuilder();
        try{
            BufferedReader br = new BufferedReader(new FileReader(file));
            String s = null;
            while((s = br.readLine())!=null){
                result.append(System.lineSeparator()+s);
				//System.out.println(s);
				//System.out.println(s.length());
            }
            br.close();    
        }catch(Exception e){
            e.printStackTrace();
        }
        return result.toString();
    }
    
    public static void main(String[] args){
        File file = new File("book.txt");
        System.out.println(txt2String(file));
    }
}

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
public class test {
	public static void main(String[] args) {
        File file = null;
        FileWriter fw = null;
        file = new File("test123.txt");
        try {
            if (!file.exists()) {
                file.createNewFile();
            }
            fw = new FileWriter(file);
            for(int i = 1;i <=3000;i++){
            fw.write("abcdefgabcdefg"+i+",");
            fw.write("sssssssssssssss"+i+",\r\n");
            fw.flush();
            }
            System.out.println("write data success ful！");
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally{
            if(fw != null){
                try {
                    fw.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
    }
}

Scanner cin=new Scanner(System.in);
int T=cin.nextInt();
String str = "1998.07.01";
String[] s = str.split("\\.");
String year = s[0];
String month = s[1];
String day = s[2];
System.out.println(year);
System.out.println(month);
System.out.println(day);

String s = "100";
 //方法一
 int a = Integer.parseInt(String s);
         Long.parseLong(String s);
         Float.parseFloat(String s);
         Double.parseDouble(String s) 
             
             
int i=11;
String s=Integer.toString(i);

javac -encoding  utf-8 BarChart.java