包java.nio.file不存在 [英] package java.nio.file does not exist

问题描述

我正在研究如何从命令行编译java。这是我所得到的：

以下是我所得到的：

 
 /myjava/compile.cmd 
 /myjava/src/a_pack/HelloWorld.java 
 /myjava/src/b_pack/Inner.java 
 /myjava/src/b_pack/Inner2.java 
 / myjava / bin 
 

HelloWorld：

 
包装a_pack; 
 
 import b_pack.Inner; 
 import b_back.Inner2; 
 import java.util.ArrayList; 
 import java.util.Iterator; 
 
 public class HelloWorld {
 
 public static void main（String [] args）{
 
 System.out.println（Hello，World ）; 
 
 Inner myInner = new Inner（）; 
 myInner.myInner（）; 
 
 Inner2 myInner2 = new Inner2（）; 
 myInner2.myInner（）; 
 
 
 ArrayList myArray = new ArrayList（）; 
 myArray.add（1）; 
 myArray.add（2）; 
 myArray.add（3）; 
 
 Iterator itr = myArray.iterator（）; 
 while（itr.hasNext（））
 {
 System.out.println（itr.next（））; 
} 
 
} 
 
} 
 

Inner.java

 
包b_pack; 
 
 public class Inner {
 
 public void myInner（）{
 System.out.println（Inner Method）; 
} 
 
} 
 

Inner2.java

 
包b_pack; 
 
 public class Inner2 {
 
 public void myInner（）{
 System.out.println（SecondInner）; 
} 
 
} 
 

我正在使用 javac进行编译 - d bin -sourcepath -src src / a_pack / HelloWorld.java
，这样可以正常工作。

现在我的理解是，因为HelloWorld.java引用了import语句中的其他包，那么javac就去编译它们。
我猜测，对于所有的java包，javac都有内部或某些东西。

无论如何 -
如果我将以下导入行添加到HelloWorld.java

import java.nio.file.Files ;

它失败与

 
 
 D：\ ..... \myjava> javac -d bin -sourcepath src src / a_pack / HelloWo 
 rld.java 
 src \a_pack\HelloWorld.java：8：package java.nio.file不存在
 import java.nio.file.Files; 
 ^ 
 1错误
 
 

这里的故事是什么？为什么有些java包好不好，有些不行？

解决方案

Java NIO 。早期版本的JDK的编译器将包含这些NIO类的任何代码。您需要升级到JDK 7或更高版本。

I'm working out how to compile java from command line at the moment. Here's what I've got:

Here's what I've got:

/myjava/compile.cmd
/myjava/src/a_pack/HelloWorld.java
/myjava/src/b_pack/Inner.java
/myjava/src/b_pack/Inner2.java
/myjava/bin

HelloWorld:

package a_pack;

import b_pack.Inner;
import b_back.Inner2;
import java.util.ArrayList; 
import java.util.Iterator; 

public class HelloWorld {

    public static void main(String[] args) {

        System.out.println("Hello, World");     

        Inner myInner = new Inner(); 
        myInner.myInner(); 

        Inner2 myInner2 = new Inner2();
        myInner2.myInner(); 


        ArrayList myArray = new ArrayList(); 
        myArray.add(1); 
        myArray.add(2); 
        myArray.add(3); 

        Iterator itr = myArray.iterator();
        while (itr.hasNext())
        {
            System.out.println(itr.next()); 
        }

    }

}

Inner.java

package b_pack; 

public class Inner {

    public void myInner() {
        System.out.println("Inner Method");
    }

}

Inner2.java

package b_pack; 

public class Inner2 {

    public void myInner() {
        System.out.println("SecondInner");
    }

}

I'm compiling this with javac -d bin -sourcepath -src src/a_pack/HelloWorld.java and this works fine.

Now my understanding is, that because the HelloWorld.java references the other packages in it's import statements, then javac goes and compiles those. And I'm guessing that for all the java packages, javac has them internally or something.

Anyway - if I add the following import line to HelloWorld.java

import java.nio.file.Files;

it fails with

D:\.....\myjava>javac -d bin -sourcepath src src/a_pack/HelloWo
rld.java
src\a_pack\HelloWorld.java:8: package java.nio.file does not exist
import java.nio.file.Files;
                    ^
1 error

What's the story here? Why are some java packages good and some not?

解决方案

Java NIO was introduced in Java 7. Compilers from earlier versions of the JDK will baulk at any code that contains these NIO classes. You need to upgrade to JDK 7 or higher.

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