Java以绝对路径和相对路径的方式读取文件

1. 绝对路径的方式读取文件

这个很简单，就是用大家熟悉的File类加载文件，然后用输入流读取文件内容就可以了。

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;

public class ReadFileTest {
	public static void main(String[] args) {
		String filename = "E:\\code\\ndctest\\src\\file\\test.txt";
		ReadFileTest readFileTest = new ReadFileTest();
		System.out.println(readFileTest.readTxt(filename));
	}

	/**
	 * 读取绝对路径文件
	 * @param filename
	 * @return
	 */
	public String readTxt(String filename) {
		File file = new File(filename);
		StringBuilder sb = new StringBuilder();
		try (InputStreamReader read = new InputStreamReader(new FileInputStream(file), "UTF-8");) {
			if (file.isFile() && file.exists()) {
				BufferedReader bufferedReader = new BufferedReader(read);
				String readLine = null;
				while ((readLine = bufferedReader.readLine()) != null) {
					sb.append(readLine);
				}
			}

		} catch (Exception e) {
			e.printStackTrace();
			System.out.println("xml数据读取错误");
		}
		return sb.toString();
	}

2. 相对路径的方式读取文件

这个其实也很简单，用到的是Class类的getResourceAsStream(String name)这个方法，返回值直接就是InputStream类型。

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;

public class ReadFileTest {
	public static void main(String[] args) {
		ReadFileTest readFileTest = new ReadFileTest();
		String filename2 = "file/test.txt";
		System.out.println(readFileTest.readTxt2(filename2));
	}

	/**
	 * 读取相对路径文件
	 * @param filename
	 * @return
	 */
	public String readTxt2(String filename){
		StringBuilder sb = new StringBuilder();
		try (InputStream is = this.getClass().getResourceAsStream(filename);
				InputStreamReader reader = new InputStreamReader(is, "UTF-8");
				BufferedReader bufferedReader = new BufferedReader(reader);) {
			String readLine = null;
			while ((readLine = bufferedReader.readLine()) != null) {
				sb.append(readLine);
			}
		} catch (Exception e) {
			e.printStackTrace();
			System.out.println("xml数据读取错误");
		}
		return sb.toString();
	}
}