Introduction to common methods of Object class

Object is the parent class of all classes and the root class of the class hierarchy. All objects (including arrays) implement the methods of this class. All objects will directly or indirectly Inherited from Object class.

(Recommended tutorial: java introductory tutorial)

Common methods of Object:

1. getClass() method: returns the class of the object when it is executed Example

public class Demo{
	public static void main(String[] args){
		Object[] arr = new Object[4];
		arr[0] = new Object();
		arr[1] = new String("字符串");
		arr[2] = new Integer(10);
		arr[3] = new Demo();

		for(Object obj: arr){
			System.out.println(obj.getClass());
		}
	}
}	

Output:

class java.lang.Object
class java.lang.String
class java.lang.Integer
class Demo

2. toString() method: Return the object as a string (if the subclass does not override the toString method, the class name @16 will be returned Hash value in hexadecimal)

public class Demo{
	public static void main(String[] args){
		Object[] arr = new Object[4];
		arr[0] = new Object();
		arr[1] = new String("字符串");
		arr[2] = new Integer(10);
		arr[3] = new Demo();

		for(Object obj: arr){
			System.out.println(obj.toString());
		}
	}
}	

Output:

java lang.Object@1db9742
字符串
10
Demo@10d69c

(Video tutorial recommendation: java video tutorial)

Rewrite toString:

@Override
public static toString(){
	return "我是demo类";
}

Output:

java lang.Object@1db9742
字符串
10
我是demo类

Modify the above code to directly output obj, and the toString() method will be called by default:

for(Object obj: arr){
	System.out.println(obj);
}

3. equals() method: compare two Whether the objects are equal

The equals method defaults to compare whether the addresses of the two objects are equal (the bottom layer uses == for comparison). Generally, the equals method is custom-written for comparison.

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