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Some commonly used methods in java

There is a newer version: 4.0.6

package com.gitee.cliveyuan.tools;

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.LineIterator;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

/**
 * 文件工具
 *
 * @author clive
 * Created on 2018/07/23
 * @since: 1.0
 */
public class FileTools extends FileUtils {

    private static final String ENCODING = "UTF-8";

    private FileTools() {
    }

    private static void validate(File file) {
        Assert.notNull(file, "file can't be null");
        Assert.isTrue(file.exists(), "file not exists: " + file.getAbsolutePath());
    }

    /**
     * 读取文件为字符串 (UTF-8模式读取)
     *
     * @param file
     * @throws IOException
     */
    public static String readFileToString(File file) throws IOException {
        validate(file);
        return readFileToString(file, ENCODING);
    }

    /**
     * 读取文件为字符串列表 (UTF-8模式读取)
     *
     * @param file
     * @throws IOException
     */
    public static List readFileToStringList(File file) throws IOException {
        return readFileToStringList(file, ENCODING);
    }

    /**
     * 读取文件为字符串列表
     *
     * @param file
     * @throws IOException
     */
    public static List readFileToStringList(File file, String encoding) throws IOException {
        validate(file);
        List list = new ArrayList<>();
        try (LineIterator lineIterator = FileUtils.lineIterator(file, encoding)) {
            while (lineIterator.hasNext()) list.add(lineIterator.nextLine());
        }
        return list;
    }

    /**
     * 获取扩展名
     *
     * @param file
     */
    public static String getExtension(File file) {
        if (Objects.isNull(file)) return null;
        return getExtension(file.getName());
    }

    /**
     * 获取扩展名
     *
     * @param filePath
     */
    public static String getExtension(String filePath) {
        return filePath.substring(filePath.lastIndexOf(".") + 1);
    }
}