MemoryLeak.java

package com.ezlippi;

import java.io.ByteArrayOutputStream;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

public class MemoryLeak {
    public static void main(String[] args) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                while (true) {
                    CustomClassLoader classLoader = new CustomClassLoader
                            ("load1", MemoryLeak.class.getClassLoader(), "com.ezlippi.MemoryLeak$Inner", "com.ezlippi.MemoryLeak$Inner$1");
                    try {
                        Class<?> innerClass = classLoader.loadClass("com.ezlippi.MemoryLeak$Inner");
                        innerClass.newInstance();
                        innerClass = null;
                        classLoader = null;
                        Thread.sleep(10);
                    } catch (ClassNotFoundException | IllegalAccessException | InstantiationException | InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }


    public static class Inner {
        private static byte[] MB = new byte[1024 * 1024];

        static ThreadLocal<Inner> threadLocal = new ThreadLocal<Inner>() {
            @Override
            protected Inner initialValue() {
                return new Inner();
            }
        };

        static {
            threadLocal.get();
        }

        public Inner() {
        }

    }

    private static class CustomClassLoader extends ClassLoader {
        private Set<String> urls;
        private String label;

        /**
         * 自定义类加载器,加载指定包名的类,其他的委托父类加载器加载
         * @param name      类加载器名称
         * @param parent    父类加载器
         * @param url       要加载的包名
         */
        public CustomClassLoader(String name, ClassLoader parent, String... url) {
            super(parent);
            this.label = name;
            this.urls = new HashSet<String>(Arrays.asList(url));
        }

        @Override
        public Class<?> findClass(String name) throws ClassNotFoundException {
            InputStream inputStream = null;
            ByteArrayOutputStream outputStream = null;
            if (urls.contains(name)) {
                try {
                    String location = name.replace('.', '/') + ".class";
                    inputStream = MemoryLeak.class.getClassLoader().getResourceAsStream(location);
                    byte[] buf = new byte[2000];
                    outputStream = new ByteArrayOutputStream();
                    int length;
                    while ((length = inputStream.read(buf)) != -1) {
                        outputStream.write(buf, 0, length);
                    }
//                    System.out.println(label + ": Loading " + name + " in " +label + " classloader");
                    byte[] data = outputStream.toByteArray();
                    return defineClass(name, data, 0, data.length);
                } catch (IOException e) {
                    throw new ClassNotFoundException(name, e);
                } finally {
                    closeStream(inputStream);
                    closeStream(outputStream);
                }
            }

            throw new ClassNotFoundException(name);
        }

        public Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
            //查看是否已经加载过
            if (findLoadedClass(name) != null) {
//                System.out.println(label + ": already loaded(" + name + ")");
                return findLoadedClass(name);
            }

            if (urls.contains(name)) {
                return findClass(name);
            } else {
//                System.out.println(label + ": super.loadclass(" + name + ")");
                //委托给父类加载器加载
                return super.loadClass(name, resolve);
            }
        }

        private void closeStream(Closeable closeable) {
            if (closeable != null) {
                try {
                    closeable.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        }

        public String toString() {
            return label;
        }
    }

}