Object Class,

Object Class,
1 Overview of Object classes

• Class Object is the root class of the class hierarchy. Each class usesObjectAs a superclass. All objects (including arrays) implement this class method.
• Object classes are constantly extracted.

 

2 equals () method

public boolean equals(Object obj)

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

 

• Example: Call the equals () method of the Object class

Package java011;/**** * Description: */public class Person {private String name; private int age; public Person () {} public Person (String name, int age) {this. name = name; this. age = age ;}}

Package java011;/***** * Description: */public class Test {public static void main (String [] args) {Person p = new Person ("James ", 15); Person p2 = new Person ("Zhang San", 15); System. out. println (p = p2); // false System. out. println (p. equals (p2); // false }}

 

• Example: override the equals () method

Package java011;/**** * Description: */public class Person {private String name; private int age; public Person () {} public Person (String name, int age) {this. name = name; this. age = age ;}@ Override public boolean equals (Object obj) {if (obj = null) {return false;} if (obj instanceof Person) {Person p = (Person) obj; if (! This. name. equals (p. name) & this. age! = P. age) {return false ;}} return true ;}}

Package java011;/***** * Description: */public class Test {public static void main (String [] args) {Person p = new Person ("James ", 15); Person p2 = new Person ("Zhang San", 15); System. out. println (p = p2); // false System. out. println (p. equals (p2); // true }}

 

3 hashcode () method

public int hashCode()

public native int hashCode();

 

Package java011;/**** * Description: */public class Person {private String name; private int age; public Person () {} public Person (String name, int age) {this. name = name; this. age = age ;}@ Override public boolean equals (Object obj) {if (obj = null) {return false;} if (obj instanceof Person) {Person p = (Person) obj; if (! This. name. equals (p. name) & this. age! = P. age) {return false ;}} return true ;}}

Package java011;/***** * Description: */public class Test {public static void main (String [] args) {Person p = new Person ("James ", 15); Person p2 = new Person ("Zhang San", 15); System. out. println (p); // java011.Person @ 1b6d3586 System. out. println (p. hashCode (); // 460141958 System. out. println (Integer. toHexString (p. hashCode (); // 1b6d3586 }}

 

4 getClass () method

public final Class<?> getClass()

public final native Class<?> getClass();

 

• Example:

Package java011;/**** * Description: */public class Person {private String name; private int age; public Person () {} public Person (String name, int age) {this. name = name; this. age = age ;}@ Override public boolean equals (Object obj) {if (obj = null) {return false;} if (obj instanceof Person) {Person p = (Person) obj; if (! This. name. equals (p. name) & this. age! = P. age) {return false ;}} return true ;}}

Package java011;/***** * Description: */public class Test {public static void main (String [] args) {Person p = new Person ("James ", 15); Class <?> Clazz = p. getClass (); System. out. println (clazz); // class java011.Person System. out. println (clazz. getName (); // java011.Person }}

 

5 toString () method

public String toString()

public String toString() {        return getClass().getName() + "@" + Integer.toHexString(hashCode());    }

 

• Example:

Package java011;/**** * Description: */public class Person {private String name; private int age; public Person () {} public Person (String name, int age) {this. name = name; this. age = age ;}@ Override public boolean equals (Object obj) {if (obj = null) {return false;} if (obj instanceof Person) {Person p = (Person) obj; if (! This. name. equals (p. name) & this. age! = P. age) {return false ;}} return true ;}}

Package java011;/***** * Description: */public class Test {public static void main (String [] args) {Person p = new Person ("James ", 15); System. out. println (p); // java011.Person @ 1b6d3586 System. out. println (p. toString (); // java011.Person @ 1b6d3586 }}