Sample code sharing of parameter passing method in java
This article mainly introduces relevant information about the detailed explanation of parameter passing methods in java. Friends who need it can refer to
Detailed explanation of parameter passing methods in java
java A classic topic faced by novices. This article is intended to end this topic. There is a saying in Java: Parameter passing in Java is passed by value. How to understand this sentence? I'm afraid it's not easy to explain it in words, and it's probably hard to understand it clearly.
Premise
Let me clarify first, the concept of by value or by reference, it comes from the C++ language, reference is not a word in the Chinese dictionary, but a C++ Concept - Do you remember the symbol "&"?
Why is there this topic? First, there is an incomplete understanding of pass-by-reference; second, many Java books and discussion arguments do not hit the mark.
In one sentence, whether to pass parameters by value or by reference, since it is a parameter passing method, it only applies to formal parameters and actual parameters. What we are talking about here is the parameter itself, not the sub-object or grandchild of the parameter object. object.
With the premise, let’s go to the c++ code:
#include <iostream>
using namespace std;
class User
{
private:
int m_id;
public:
User(int id=0){m_id = id;}
void setId(int id){m_id = id;}
int getId(){return m_id;}
};
void test0(User t){//按值传参
User s;
t = s;
t.setId(1002);
cout << "test1:" << t.getId() << endl;
}
void test1(User *t){//按值传参
t = new User();//指针指向了一个新对象，外面实参没变
t->setId(1002);
cout << "test1:" << t->getId() << endl;
}
void test2(User* & t){//按引用传参
t = new User();//指针指向了一个新对象，外面实参也跟着变了
t->setId(1002);
cout << "test2:" << t->getId() << endl;
}
int main(int argc, char const *argv[]) {
cout<< "\npass by ref:"<<endl;
User* t = new User();
t->setId(1001);
cout << t->getId() << endl;
test2(t);
cout << t->getId() << endl;
cout<< "\npass by value:"<<endl;
t = new User();
t->setId(1001);
cout << t->getId() << endl;
test1(t);
cout << t->getId() << endl;
return 0;
}Output result:
pass by ref: 1001 test2:1002 1002 pass by value: 1001 test1:1002 1001
c++ summary:
Pass by value, then the formal parameters are modified within the function to point to a new object, and the external actual parameters are not affected.
Pass by reference, then the formal parameters are modified within the function to point to a new object, and the external actual parameters are also changed.
Aimed to illustrate the problem, the code may have a memory leak.
Go to java:
package com.pollyduan.bean;
@Data
public class User {
private Integer id;
public static void testObject(User t){
t=new User();//指向了一个新对象，外面实参没变
t.setId(1002);
System.out.println("testObject="+t);
}
@Test
public void testObject(){
User user=new User();
user.setId(1001);
System.out.println("user="+user);
testObject(user);
System.out.println("user="+user);
}
}Output result:
user=User(id=1001) testObject=User(id=1002) user=User(id=1001)
java summary:
With c++ Compare the logic and make your own decision.
The above is the detailed content of Sample code sharing of parameter passing method in java. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
Break or return from Java 8 stream forEach?
Feb 07, 2025 pm 12:09 PM
Java 8 introduces the Stream API, providing a powerful and expressive way to process data collections. However, a common question when using Stream is: How to break or return from a forEach operation? Traditional loops allow for early interruption or return, but Stream's forEach method does not directly support this method. This article will explain the reasons and explore alternative methods for implementing premature termination in Stream processing systems. Further reading: Java Stream API improvements Understand Stream forEach The forEach method is a terminal operation that performs one operation on each element in the Stream. Its design intention is
PHP: A Key Language for Web Development
Apr 13, 2025 am 12:08 AM
PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7
PHP vs. Python: Understanding the Differences
Apr 11, 2025 am 12:15 AM
PHP and Python each have their own advantages, and the choice should be based on project requirements. 1.PHP is suitable for web development, with simple syntax and high execution efficiency. 2. Python is suitable for data science and machine learning, with concise syntax and rich libraries.
PHP vs. Other Languages: A Comparison
Apr 13, 2025 am 12:19 AM
PHP is suitable for web development, especially in rapid development and processing dynamic content, but is not good at data science and enterprise-level applications. Compared with Python, PHP has more advantages in web development, but is not as good as Python in the field of data science; compared with Java, PHP performs worse in enterprise-level applications, but is more flexible in web development; compared with JavaScript, PHP is more concise in back-end development, but is not as good as JavaScript in front-end development.
PHP vs. Python: Core Features and Functionality
Apr 13, 2025 am 12:16 AM
PHP and Python each have their own advantages and are suitable for different scenarios. 1.PHP is suitable for web development and provides built-in web servers and rich function libraries. 2. Python is suitable for data science and machine learning, with concise syntax and a powerful standard library. When choosing, it should be decided based on project requirements.
Java Program to Find the Volume of Capsule
Feb 07, 2025 am 11:37 AM
Capsules are three-dimensional geometric figures, composed of a cylinder and a hemisphere at both ends. The volume of the capsule can be calculated by adding the volume of the cylinder and the volume of the hemisphere at both ends. This tutorial will discuss how to calculate the volume of a given capsule in Java using different methods. Capsule volume formula The formula for capsule volume is as follows: Capsule volume = Cylindrical volume Volume Two hemisphere volume in, r: The radius of the hemisphere. h: The height of the cylinder (excluding the hemisphere). Example 1 enter Radius = 5 units Height = 10 units Output Volume = 1570.8 cubic units explain Calculate volume using formula: Volume = π × r2 × h (4
PHP: The Foundation of Many Websites
Apr 13, 2025 am 12:07 AM
The reasons why PHP is the preferred technology stack for many websites include its ease of use, strong community support, and widespread use. 1) Easy to learn and use, suitable for beginners. 2) Have a huge developer community and rich resources. 3) Widely used in WordPress, Drupal and other platforms. 4) Integrate tightly with web servers to simplify development deployment.
PHP's Impact: Web Development and Beyond
Apr 18, 2025 am 12:10 AM
PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip
