import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;

public class ManualClear {

 public static void main(String[] args) {
  FileInputStream fileInputStream = null;
  try {
   fileInputStream = new FileInputStream("./src/ManualClear.java");
  } catch (FileNotFoundException e) {
   System.out.println(e.getMessage());
   e.printStackTrace();
   return;
  }

  try {
   byte[] bbuf = new byte[1024];
   int hasRead = 0;
   try {
    while ((hasRead = fileInputStream.read(bbuf)) > 0) {
     System.out.println(new String(bbuf, 0, hasRead));
    }
   } catch (IOException e) {
    e.printStackTrace();
   }
  } finally {
   try {
    fileInputStream.close();
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
 }

}

import java.util.Arrays;
import java.util.EmptyStackException;

class Stack{
 private Object[] elements;
 private int size;
 private static final int DEFAULT_INITAL_CAPACITY = 16;
 
 public Stack() {
  elements = new Object[DEFAULT_INITAL_CAPACITY];
 }
 
 public void push(Object e){
  ensureCapacity();
  elements[size++] = e;
 }
 
 public Object pop() {
  if (size == 0) {
   throw new EmptyStackException();
  }
  
  return elements[--size];
 }
 
 private void ensureCapacity() {
  if (elements.length == size) {
   elements = Arrays.copyOf(elements, 2 * size + 1);
  }
 }
}

public class StackDemo {
 
 public static void main(String[] args) {
  Stack stack = new Stack();
  
  for (int i = 0; i < 10000; i++) {
   stack.push(new Object());
  }
  
  for(int i = 0; i < 10000; i++) {
   stack.pop();
  }
 }

}

class Book {
 boolean checkout = false;
 public Book(boolean checkout) {
  this.checkout = checkout;
 }
 
 public void checkin(){
  checkout = false;
 }
 
 @Override
 protected void finalize() throws Throwable {
  if (checkout) {
   System.out.println("Error: check out");
  }
 }
}

public class FinalizeCheckObjectUse {

 public static void main(String[] args) {
  new Book(true);
  System.gc();
 }

}

class Parent{
  @Override
  protected void finalize() throws Throwable {
    System.out.println(getClass().getName() + " finalize start");
  }
}

class Son extends Parent{
  @Override
  protected void finalize() throws Throwable {
    System.out.println(getClass().getName() + " finalize start");
  }
}
public class SuperFinalizeLost {

  public static void main(String[] args) {
    new Son();
    System.gc();
  }

}

class Parent{
  @Override
  protected void finalize() throws Throwable {
    System.out.println(getClass().getName() + " finalize start");
  }
}

class Son extends Parent{
  @Override
  protected void finalize() throws Throwable {
    System.out.println(getClass().getName() + " finalize start");
    int i = 5 / 0;
    super.finalize();
  }
}
public class SuperFinalizeLost {

  public static void main(String[] args) {
    new Son();
    System.gc();
  }

}

class Parent2{
  private final Object finalizeGuardian = new Object() {
    protected void finalize() throws Throwable {
      System.out.println("在此执行父类终结方法中的逻辑");
    };
  };
}

class Son2 extends Parent2{
  @Override
  protected void finalize() throws Throwable {
    System.out.println(getClass().getName() + " finalize start");
    int i = 5 / 0;
    super.finalize();
  }
}

public class FinalizeGuardian {

  public static void main(String[] args) {
    new Son2();
    System.gc();
  }

}