java - Java中finalize方法的问题

Question

这个问题已经有答案了:

When is the finalize() method called in Java? (18 个回答)

已关闭 4 年前。

在我上次的练习中，我一直在使用 Finalize 方法时遇到问题。似乎我有一个已弃用的方法，而且我似乎找不到最新版本的 Finalize。我有两个文件，需要调用“finalize”方法。有人可以给我一个完成方法的例子或者帮助我完成我的方法吗？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

finalize 自 Java 9 起已被弃用。您可以在 javadoc 中了解原因以及替代方案。 :-

Deprecated. The finalization mechanism is inherently problematic. Finalization can lead to performance issues, deadlocks, and hangs. Errors in finalizers can lead to resource leaks; there is no way to cancel finalization if it is no longer necessary; and no ordering is specified among calls to finalize methods of different objects. Furthermore, there are no guarantees regarding the timing of finalization. The finalize method might be called on a finalizable object only after an indefinite delay, if at all. Classes whose instances hold non-heap resources should provide a method to enable explicit release of those resources, and they should also implement AutoCloseable if appropriate. The Cleaner and PhantomReference provide more flexible and efficient ways to release resources when an object becomes unreachable.

您不应该使用此方法。实际上你不需要!

如果您仍然想使用它，请忽略警告或在您的方法中添加以下内容以隐藏警告:-

@SuppressWarnings( "deprecation" )