Java常用类
1.Object类
java.lang.Object
类 Object 是类层次结构的根类。每个类都使用 Object 作为超类。所有对象（包括数组）都实现这个类的方法。
常用方法：
public native int hashCode();
返回该对象的哈希码值
public String toString() {
return getClass().getName() + "@" + Integer.toHexString(hashCode());
}
返回该对象的字符串表示。建议所有子类都重写此方法。
public boolean equals(Object obj) {
return (this == obj);
}
返回其他某个对象是否与此对象“相等”。
注意：当此方法被重写时，通常有必要重写 hashCode 方法，以维护 hashCode 方法的常规协定，该协定声明相等对象必须具有相等的哈希码。
String类重写了equals()和hashCode()方法，可以参考
protected void finalize() throws Throwable {}
当垃圾回收器确定不存在对该对象的更多引用时，由对象的垃圾回收器调用此方法。子类重写 finalize 方法，以配置系统资源或执行其他清除。
protected native Object clone() throws CloneNotSupportedException;
创建并返回此对象的一个副本.所有要进行"克隆"的对象所属的类必须实现java.lang.Cloneable接口．下面给出一个实例实现深度拷贝功能：
/**
* clone()方法的应用
*/
package com.java.basic;
/**
* @author Administrator
*
*/
class Person implements Cloneable {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Person() {
super();
}
public Person(String name, int age) {
this();
this.name = name;
this.age = age;
}
@Override
public String toString() {
// TODO Auto-generated method stub
return "Name:" + this.name + "\tAge:" + age;
}
@Override
public Object clone() {
Person p = null;
try {
p = (Person) super.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
return p;
}
}
/**
* clone()方法的应用
*/
package com.java.basic;
/**
* @author Administrator
*
*/
public class Book implements Cloneable {
String bookName;
double price;
Person author;
public Book(String bookName, double price, Person author) {
super();
this.bookName = bookName;
this.price = price;
this.author = author;
}
@Override
public Object clone() {
Book book = null;
try {
book = (Book) super.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
book.author = (Person) this.author.clone();
return book;
}
@Override
public String toString() {
// TODO Auto-generated method stub
return "bookName:" + bookName + "\t" + "price:" + price + "\t" + author;
}
}
/**
* 深度clone()方法的测试
*/
package com.java.basic;
public class TestDeepCopy {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Book b1 = new Book("Java编程", 30.50, new Person("张三", 34));
Book b2 = (Book) b1.clone();
b2.price = 44.0;
b2.author.setAge(45);
b2.author.setName("李四");
b2.bookName = "Java开发";
System.out.println(b1);
System.out.println(b2);
}
}
