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java基础—Objcet中的equals方法重写

JAVA方法基础重写 equals
2023-09-11 14:14:53 时间 



package mytest;

public class Test1

{

	public static void main(String[] args) 
	{
		Person p1 = new Person(20);
		Person p2 = new Person(30);
		System.out.println(p1.equals(p2));//false
		
	}

}
class Person
{
	private int age;
	Person(int age)
	{
		this.age = age;
	}
	}

重写equals方法后： 


package mytest;

public class Test1

{

	public static void main(String[] args) 
	{
		Person p1 = new Person(20);
		Person p2 = new Person(20);
		
		System.out.println(p1.equals(p2));//true
		
	}

}
class Person
{
	private int age;
	Person(int age)
	{
		this.age = age;
	}
	
	public boolean equals(Object obj)
	{
		if(!(obj instanceof Person))
		{
			throw new ClassCastException("类型错误");
		}
		Person p = (Person)obj;
		
		return this.age==p.age;
	}
	
	}

Objcet 类的toString方法  默认的返回的内容是“对象所属的类名  和 对象的哈希值” 

package mytest;

public class Test1

{

	public static void main(String[] args) 
	{
		Person p1 = new Person(20);
		Person p2 = new Person(20);
		
		System.out.println(p1.equals(p2));//true
		System.out.println(p1.toString());//mytest.Person@37
		System.out.println(p2.toString());//mytest.Person@37
		
	}

}
class Person
{
	private int age;
	Person(int age)
	{
		this.age = age;
	}
	
	public boolean equals(Object obj)
	{
		if(!(obj instanceof Person))
		{
			throw new ClassCastException("类型错误");
		}
		Person p = (Person)obj;
		
		return this.age==p.age;
	}
	public int hashCode()
	{
		return 55;
	}
	
	}



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