java io学习之File类

Posted 2020-08-14 woqiaoxun

1.先看下四个静态变量

static String	pathSeparator The system-dependent path-separator character, represented as a string for convenience.
static char	pathSeparatorChar The system-dependent path-separator character.
static String	separator The system-dependent default name-separator character, represented as a string for convenience.
static char	separatorChar The system-dependent default name-separator character.

由于windows和unix内核的系统路径表示方式不一致（windows为‘\‘，unix内核的为‘/‘），所以java提供了公用的路径分割符，根据不同的系统自动变换，但是在实际使用中，都使用‘/‘，windows和unix内核系统都支持。

Linux下测试

public class FileTest {
    public static void main(String[] args) {
        System.out.println(File.pathSeparator);
        System.out.println(File.pathSeparatorChar);
        System.out.println(File.separator);
        System.out.println(File.separatorChar);
    }
}

输出

:
:
/
/

 

2.File类的构造方法

File(File parent, String child) Creates a new File instance from a parent abstract pathname and a child pathname string.

File(String pathname) Creates a new File instance by converting the given pathname string into an abstract pathname.

File(String parent, String child) Creates a new File instance from a parent pathname string and a child pathname string.

File(URI uri) Creates a new File instance by converting the given file: URI into an abstract pathname.

第一种

    @Test
    public void test1() throws Exception{
        File parent = new File("/joey/soft");
        File son = new File(parent,"son.txt");
        System.out.println(son.getAbsolutePath());
        System.out.println(son.getParent());
        System.out.println(parent.getName());
    }

输出

/joey/soft/son.txt
/joey/soft
soft

第二种

    @Test
    public void test2() throws Exception{
        File son = new File("/joey/soft/son.txt");
        System.out.println(son.getAbsolutePath());
        System.out.println(son.getParent());
    }

输出

/joey/soft/son.txt
/joey/soft

第三种

    @Test
    public void test3() throws Exception{
        File son = new File("/joey/soft","son.txt");
        System.out.println(son.getAbsolutePath());
        System.out.println(son.getParent());
    }

输出：

/joey/soft/son.txt
/joey/soft

 

第四种

    @Test
    public void test4() throws Exception{
        File f = new File("/joey/soft","son.txt");
        File son = new File(f.toURI());
        System.out.println(son.getAbsolutePath());
        System.out.println(son.getParent());
    }    

输出

/joey/soft/son.txt
/joey/soft

 

当然也可以不写绝对路径，写相对路径。

@Test
    public void test5() throws Exception{
        File son = new File("test.txt");
        System.out.println(son.getAbsolutePath());
        System.out.println(son.getParent());
    }

输出

/home/joey/eclipse/workspace/IOTest/test.txt
null

 

参考：http://docs.oracle.com/javase/7/docs/api/java/io/File.html#File(java.net.URI)