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POJava: static-non-static-this problem
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  1. POJava: static-non-static-this problem
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    copied!<pre><code>$ javac TestFilter.java TestFilter.java:19: non-static variable this cannot be referenced from a static context for(File f : file.listFiles(this.filterFiles)){ ^ 1 error $ sed -i 's@this@TestFilter@g' TestFilter.java $ javac TestFilter.java $ java TestFilter file1 file2 file3 </code></pre> <p><strong>TestFilter.java</strong></p> <pre><code>import java.io.*; import java.util.*; public class TestFilter { private static final FileFilter filterFiles; // STATIC! static{ filterFiles = new FileFilter() { // Not Static below. When static, an error: // "accept(java.io.File) in cannot implement // accept(java.io.File) in java.io.FileFilter; // overriding method is static" // // I tried to solve by the change the problem at the bottom. public boolean accept(File file) { return file.isFile(); } }; } // STATIC! public static void main(String[] args){ HashSet&lt;File&gt; files = new HashSet&lt;File&gt;(); File file = new File("."); // IT DID NOT WORK WITH "This" but with "TestFilter". // Why do I get the error with "This" but not with "TestFilter"? for(File f : file.listFiles(TestFilter.filterFiles)){ System.out.println(f.getName()); files.add(f); } } } </code></pre> <p><strong>Update: define "current object"</strong></p> <p>Constructor created, object created but the <code>this</code> does not refer to the <em>current object</em> "test". It works when I change this to "test" but it does not work with "this". Why?</p> <pre><code>$ javac TestFilter.java TestFilter.java:28: non-static variable this cannot be referenced from a static context for(File f : this.getFiles()){ ^ 1 error $ cat TestFilter.java import java.io.*; import java.util.*; public class TestFilter { private static final FileFilter filterFiles; private HashSet&lt;File&gt; files; static{ filterFiles = new FileFilter() { public boolean accept(File file) { return file.isFile(); } }; } TestFilter(){ files = new HashSet&lt;File&gt;(); File file = new File("."); for(File f : file.listFiles(filterFiles)){ files.add(f); } } public static void main(String[] args){ // CONSTRUCTOR with no pars invoked and object "test" created here! TestFilter test = new TestFilter(); // Why does it not work with "this"? // "test" is surely the current object. for(File f : this.getFiles()){ System.out.println(f.getName()); } } public HashSet&lt;File&gt; getFiles() { return files; } } </code></pre>
 

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