Article directory
Table of contents
1.2 Rewrite the toString method
foreword
Hello everyone, I love animal milk the most. Today I will tell you about objects in java and the tool objects of objects.
So, follow me to have a look!
1. What is Object?
Object is the top-level parent class in java, all classes will directly or indirectly inherit Object
2. Common methods of Object
1.tostring
1.1 return value
Above we see that the toString method in the parent class Object returns a string of unknown strings, so when we use the toString method, we need to rewrite the toString method
1.2 Rewrite the toString method
2.equals
For detailed usage and analysis of equals, please refer to http://t.csdn.cn/QauYZ
3. clone (clone)
1. Clone interface
In java, if you want to clone an object, you must implement the clone interface Cloneable
The above cloning text explanation is a bit wrong, add:
Shallow copy means that when copying an object, only its reference is copied, not the object itself. That is to say, the copied object and the original object share the same reference, and they point to the same object. In this case, if the attribute value of the copied object is modified, the attribute value of the original object will be affected.
Deep copy refers to copying an object, not only copying its reference, but also copying the object itself. In other words, the copied object and the original object are two independent objects, and their attribute values do not affect each other.
Verify that the clone method of the parent class is a shallow copy
At this time, someone may ask
Isn't String a reference data type? Shouldn't the reference data type be a deep copy?
Why is it also a shallow copy? In fact, this is related to the immutability of String
三.Objects
As the name suggests, the tool class of object
Object is an object tool class that provides some methods
public static boolean equals(Object a, Object b)
public static boolean isNull(Object obj)
Determine whether the object is null, return true for null1, otherwise return false
public static boolean nonNull(Object obj)
Determine whether the object is null, opposite to the result of isNull
equals will not be introduced here
Summarize
The above is the main content of this blog post. You should focus on understanding toString, equals, clone
