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📜  java object类

📅  最后修改于: 2020-09-24 05:35:21             🧑  作者: Mango

Java中的对象类

默认情况下，Object类是Java中所有类的父类。换句话说，它是Java的最高类。

如果要引用其类型未知的任何对象，则Object类很有用。请注意，父类引用变量可以引用子类对象，称为向上转换。

让我们举个例子，有一个getObject()方法返回一个对象，但是它可以是任何类型，例如Employee，Student等，我们可以使用Object类引用来引用该对象。例如：

"Object obj=getObject();//we don't know what object will be returned from this method

Object类为所有对象提供了一些常见的行为，例如可以比较对象，可以克隆对象，可以通知对象等。

对象类的方法

The Object class provides many methods. They are as follows:
Method Description
public final Class getClass() returns the Class class object of this object. The Class class can further be used to get the metadata of this class.
public int hashCode() returns the hashcode number for this object.
public boolean equals(Object obj) compares the given object to this object.
protected Object clone() throws CloneNotSupportedException creates and returns the exact copy (clone) of this object.
public String toString() returns the string representation of this object.
public final void notify() wakes up single thread, waiting on this object’s monitor.
public final void notifyAll() wakes up all the threads, waiting on this object’s monitor.
public final void wait(long timeout)throws InterruptedException causes the current thread to wait for the specified milliseconds, until another thread notifies (invokes notify() or notifyAll() method).
public final void wait(long timeout,int nanos)throws InterruptedException causes the current thread to wait for the specified milliseconds and nanoseconds, until another thread notifies (invokes notify() or notifyAll() method).
public final void wait()throws InterruptedException causes the current thread to wait, until another thread notifies (invokes notify() or notifyAll() method).
protected void finalize()throws Throwable is invoked by the garbage collector before object is being garbage collected.

在下一章中，我们将详细学习这些方法。