判斷ClassLoader下的某個類是否有重複[轉自梁飛]

import java.net.URL;
import java.util.*;

public class etst {

    public static void checkDuplicate(Class cls) {
        checkDuplicate(cls.getName().replace('.', '/') + ".class");
    }

    public static void checkDuplicateByName(String className) {
        System.err.println("checkDuplicate");
        checkDuplicate(className.replace('.', '/') + ".class");
    }

    public static void checkDuplicate(String path) {
        try {
            // 在ClassPath搜文件
            System.err.println("checkDuplicate");
            Enumeration<URL> urls = Thread.currentThread().getContextClassLoader().getResources(
                    path);
            Set files = new HashSet();
            while (urls.hasMoreElements()) {
                URL url = urls.nextElement();
                if (url != null) {
                    String file = url.getFile();
                    if (file != null && file.length() > 0) {
                        System.err.println("Duplicate class " + path + " in " + files.size()
                                + " jar " + url);
                        files.add(file);
                    }
                }
            }
            // 如果有多個，就表示重複
            if (files.size() > 1) {
                System.err.println("Duplicate class " + path + " in " + files.size() + " jar "
                        + files);
            }
        } catch (Throwable e) { // 防禦性容錯
            System.err.println(e.getMessage());
        }
    }
    
    
    public static void main(String[] args){
        checkDuplicateByName("java.lang.String");
    }

}

 

輸出結果：

checkDuplicate
checkDuplicate
Duplicate class java/lang/String.class in 0 jar jar:file:/usr/lib/jvm/java-6-sun-1.6.0.24/jre/lib/rt.jar!/java/lang/String.class