IO文件的创建，写入和读取

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
@SuppressWarnings("all")
public class IoDemo {
	public static void main(String[] args) {
		File file = new File("D:/java4/text.txt");
		//创建文件夹
		if(!file.getParentFile().exists()) {
			file.getParentFile().mkdirs();
			System.out.println("文件夹创建成功！");
		}
		//创建文件
		if(!file.exists()) {
			try {
				file.createNewFile();
				System.out.println("文件创建成功！");
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}	
		}
		Writer w = null;
		try {
			w = new FileWriter(file);
			w.write("我好慌！aaa");
			w.flush();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {
			try {
				w.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		System.out.println(file.canRead() ? "文件可读" : "文件不可读");
		
		Reader r = null;
		char[] ch = new char[1024];
		StringBuffer sbf = null;
		try {
			r = new FileReader(file);
			try {
				sbf = new StringBuffer();
				int length = r.read(ch);//将字符读入char[]中
				System.out.println(length);
				while(length != -1) {
					sbf.append(ch);
					length = r.read(ch);
					System.out.println(length);
				}
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}finally {
			try {
				r.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		System.out.println(sbf);
		
	}

}