Java学习之常用类（三.Math类；四File类 五.枚举类型）

boolean

isFile

()

package bjsxt;//注意：打包后的父路径不是bjsxt，它会把bjsxt作为一起java bjsxt.TestFile.java

import java.io.*;

public class TestFile {

public static void main(String[] args) {

String separator = File.separator;

String filename = "myfile.txt";

String directory = "mydir1" + separator + "mydir2";

//String directory = "mydir1/mydir2";

//String directory = "mydir1\\mydir2";

File f = new File(directory, filename);

if (f.exists()) {

System.out.println("文件名：" + f.getAbsolutePath());

System.out.println("文件大小：" + f.length());

} else {

f.getParentFile().mkdirs();//求包上层的上层路径

try {

f.createNewFile();

} catch (IOException e) {

e.printStackTrace();

}

}

}

}

import java.io.*;

public class FileList{

public static void main(String args[]){

File f = new File("d:/java/S");

System.out.println(f.getName());

tree(f,1);

}

private static void tree(File f,int level){

String preStr = "";

for(int i=0;i<level;i++){

preStr +=" ";

}

File[] childs = f.listFiles();

for(int i=0;i<childs.length;i++){

System.out.println(preStr+childs[i].getName());

if(childs[i].isDirectory()){

tree(childs[i],level+1);

}

}

}

}

public class TestEnum {

public enum MyColor { red, green, blue };

public enum MyDoorOpener {me, mywife};

public static void main(String[] args) {

MyColor m = MyColor.red;

switch(m) {

case red:

System.out.println("red");

break;

case green:

System.out.println("green");

break;

default:

System.out.println("default");

}

System.out.println(m);

}

}