Java中的finalize方法的问题

Question

这个问题已经在这里有了答案：

• 什么时候在Java中调用finalize（）方法？ 16个答案

在上一次练习中，我对finalize方法遇到了问题。 好像我有一个过时的方法，而且我似乎找不到finalize的最新版本。 我有两个文件，需要调用“ finalize”方法。 有人可以给我一个确定方法的例子还是可以帮助我？ 这是我的代码：

public class RoomOccupancy {

    private int numberInRoom;
    private static int totalNumber;
    private double roomCharges;
    private boolean finalizeCalled;

    public RoomOccupancy () {
        this.numberInRoom = 0;
        this.totalNumber = 0;
        this.roomCharges = 0;
        this.finalizeCalled = false;
        System.out.println ( "Room Occupancy - default/no argument constructor" );
    }

    public RoomOccupancy (int number, double rCharges) {
        numberInRoom = number;
        roomCharges = rCharges;
        finalizeCalled = false;
        System.out.println ( "Room Occupancy - Overloaded/2-argument constructor" );
    }

    public static int getTotal () {
        return totalNumber;
    }

    public void addOneToRoom () {
        numberInRoom++;
        totalNumber++;
    }

    public void removeOneFromRoom () {
        numberInRoom--;
        totalNumber--;
    }

    public int getNumber () {
        return numberInRoom;
    }

    public void setNumber (int number) {
        this.numberInRoom = number;
    }

    public double getCharges () {
        return roomCharges;
    }

    public void setCharges (double rCharges) {
        this.roomCharges = rCharges;
    }

    public String toString () {
        String c;
        c = " " + numberInRoom + " " + roomCharges + " ";
        return c;
    }

    public boolean equals ( Object obj ) {
        if ( this == obj ) return true;

        if (( obj != null) && ( getClass() == obj.getClass())) {
            RoomOccupancy d = ( RoomOccupancy ) obj;

            if (( numberInRoom == d.numberInRoom) &&
                ( totalNumber == d.totalNumber) &&
                ( roomCharges == d.roomCharges)) {
                return true;
            }
            else {
                return false;
            }

        }
        else {
            return false;
        }

    }

    public void finalize ( ) {
        if ( !finalizeCalled ) {
            // Do cleanup
        }
        System.out.println ( "Course - finalize method" );

    }

    public void dispose ( ) {
        //Do cleanup
        finalizeCalled = true;
        System.out.println ( "Course - finalize method" );
    }
}

import java.text.DecimalFormat;

public class RoomOccupancyTest {

    public static void main ( String [] args ) {

        RoomOccupancy noOccupancy = new RoomOccupancy ( );
        System.out.println ("No Occupancy =" + noOccupancy);
        RoomOccupancy roomA = new RoomOccupancy(0, 100.00);
        RoomOccupancy roomB = new RoomOccupancy(0, 200.00);
        RoomOccupancy roomC = new RoomOccupancy(0, 250.00);
        DecimalFormat patternCharges = new DecimalFormat("#####0.00");

        System.out.println ("Five people have checked into room A at $100.00 per person\n" +
                            "Four people have checked into room B at $200.00 per person.\n" +
                            "Three people have checked into room C at $250.00 per person.");
        roomA.addOneToRoom();
        roomA.addOneToRoom();
        roomA.addOneToRoom();
        roomA.addOneToRoom();
        roomA.addOneToRoom();
        roomB.addOneToRoom();
        roomB.addOneToRoom();
        roomB.addOneToRoom();
        roomB.addOneToRoom();
        roomC.addOneToRoom();
        roomC.addOneToRoom();
        roomC.addOneToRoom();

        System.out.println ("Room A holds " + roomA.getNumber() + " The total charge is: $" + (patternCharges.format(roomA.getCharges() * roomA.getNumber())));
        System.out.println ("Room B holds " + roomB.getNumber() + " The total charge is: $" + (patternCharges.format(roomB.getCharges() * roomB.getNumber())));
        System.out.println ("Room C holds " + roomC.getNumber() + " The total charge is: $" + (patternCharges.format(roomC.getCharges() * roomC.getNumber())));
        System.out.println ("Total in all rooms is " + RoomOccupancy.getTotal());

        System.out.println ("One person from each room has left.");
        roomA.removeOneFromRoom();
        roomB.removeOneFromRoom();
        roomC.removeOneFromRoom();

        System.out.println ("Room A holds " + roomA.getNumber() + " The total charge is: $" + (patternCharges.format(roomA.getCharges() * roomA.getNumber())));
        System.out.println ("Room B holds " + roomB.getNumber() + " The total charge is: $" + (patternCharges.format(roomB.getCharges() * roomB.getNumber())));
        System.out.println ("Room C holds " + roomC.getNumber() + " The total charge is: $" + (patternCharges.format(roomC.getCharges() * roomC.getNumber())));
        System.out.println ("Total in all rooms is " + RoomOccupancy.getTotal());

        if (roomA == roomB)
            System.out.println ("Room A and B are the same object."); // NOT EXPECTED
        if (roomA == roomC)
            System.out.println ("Room A and C are the same object."); // NOT EXPECTED
        if (roomB == roomC)
            System.out.println ("Room B and C are the same object."); // NOT EXPECTED
        else
            System.out.println ("No rooms are the same object."); // EXPECTED

        if (roomA.equals (roomB))
            System.out.println ( "Room A and B are EQUAL."); // NOT EXPECTED
        if (roomA.equals(roomC))
            System.out.println ( "Room A and C are the EQUAL."); // NOT EXPECTED
        if (roomB.equals(roomC))
            System.out.println ( "Room B and C are the EQUAL."); // NOT EXPECTED
        else
            System.out.println ( "No Rooms are EQUAL."); // EXPECTED

        roomA.finalize();
        roomB.finalize();
        roomC.finalize();

        roomA = roomB = roomC = null;
        System.gc();


    }
}

Answer 1

从Java 9开始不推荐使用finalize 。您可以在javadoc中看到原因和替代方法：-

不推荐使用 。 最终确定机制本质上存在问题。 终结处理可能会导致性能问题，死锁和挂起。 终结器中的错误可能导致资源泄漏； 如果不再需要取消终结，则无法取消； 并且在用于终结不同对象的方法的调用之间未指定任何顺序。 此外，无法保证最终确定的时间。 只有在不确定的延迟之后（如果有的话），才可以在可终结对象上调用finalize方法。 其实例拥有非堆资源的类应提供一种方法来启用这些资源的显式释放，并且在适当时，它们还应实现AutoCloseable。 当对象变得不可访问时，Cleaner和PhantomReference提供了更灵活和有效的方式来释放资源。

您不应该使用此方法。 实际上，您不需要！

如果仍要使用它，请忽略该警告或在您的方法上添加以下内容以隐藏警告：

@SuppressWarnings( "deprecation" )