Recursion

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Recursion

Recursion

  1. 所谓递归(Recursion),就是方法调用自身。对于递归来说，一定有一个出口，让递归借宿，只有这样才能保证不出现死循环。
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public class Test {
    public int compute(int numnber) {
        if (numnber == 1) {
            return 1;
        } else {
            return numnber * compute(numnber - 1);
        }
    }
    public static void main(String[] args) {
        Test test = new Test();
        System.out.println(test.compute(5));
    }
}
public class FileTest {
    public static void deleteAll(File file) {
        if (file.isFile() || file.list().length == 0) {
            file.delete();
        } else {
            File[] files = file.listFiles();
            for (File file1 : files) {
                deleteAll(file1);
                file.delete();
            }
        }
    }
    public static void main(String[] args) {
        File file = new File("/Users/bob/Downloads/activiti-5.16.41");
        deleteAll(file);
    }
}
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/**
 * 循环遍历文件夹
 */
public class ListAllTest {
    //用于判断目录或文件所处的层次
    private static int time;
    public static void deepList(File file) {
        if (file.isFile() || file.listFiles().length == 0) {
            return;
        } else {
            File[] files = file.listFiles();
            files = sort(files);
            for (File file1 : files) {
                StringBuffer stringBuffer = new StringBuffer();
                if (file1.isFile()) {
                    stringBuffer.append(getTabs(time));
                    stringBuffer.append(file1.getName());
                } else {
                    stringBuffer.append(getTabs(time));
                    stringBuffer.append(file1.getName());
                    stringBuffer.append("\\");
                }
                System.out.println(stringBuffer.toString());
                if (file1.isDirectory()) {
                    time++;
                    deepList(file1);
                    time--;
                }
            }
        }
    }
    //整理文件数组，使得目录排在文件之前
    private static File[] sort(File [] files){
        List<File> list = new ArrayList<>();
        for (File file : files) {
            if (file.isDirectory()) {
                list.add(file);
            }
        }
        for (File file : files) {
            if (file.isFile()) {
                list.add(file);
            }
        }
        return list.toArray(new File[files.length]);
    }
    //判断需要加多少个tab
    private static String getTabs(int time) {
        StringBuffer stringBuffer = new StringBuffer();
        for (int i = 0; i < time; i++) {
            stringBuffer.append("\t");
        }
        return stringBuffer.toString();
    }
    public static void main(String[] args) {
        File file = new File("/Users/bob/Downloads/activiti-5.16.4");
        deepList(file);
    }
}