Java 通过引用传递

编程入门行业动态更新时间:2024-10-28 08:28:49

本文介绍了Java 通过引用传递的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！问题描述

这两个代码有什么区别:

What is the difference between this 2 codes:

代码 A:

Foo myFoo; myFoo = createfoo();

哪里

public Foo createFoo() { Foo foo = new Foo(); return foo; }

对比.代码 B:

Foo myFoo; createFoo(myFoo); public void createFoo(Foo foo) { Foo f = new Foo(); foo = f; }

这两段代码有什么区别吗?

Are there any differences between these 2 pieces of codes?

推荐答案

Java 总是按值而不是按引用传递参数.

Java always passes arguments by value NOT by reference.

让我通过一个示例来解释:

public class Main { public static void main(String[] args) { Foo f = new Foo("f"); changeReference(f); // It won't change the reference! modifyReference(f); // It will modify the object that the reference variable "f" refers to! } public static void changeReference(Foo a) { Foo b = new Foo("b"); a = b; } public static void modifyReference(Foo c) { c.setAttribute("c"); } }

我将分步解释:

声明一个名为 f 的类型为 Foo 的引用，并将其分配给一个类型为 Foo 的新对象，并带有一个属性 "f".

Declaring a reference named f of type Foo and assign it to a new object of type Foo with an attribute "f". Foo f = new Foo("f");

在方法方面，声明了一个名为 a 的 Foo 类型的引用，并且它最初被分配给 null.

From the method side, a reference of type Foo with a name a is declared and it's initially assigned to null.

public static void changeReference(Foo a)

当您调用方法 changeReference 时，引用 a 将分配给作为参数传递的对象.

As you call the method changeReference, the reference a will be assigned to the object which is passed as an argument.

changeReference(f);

声明一个名为 b 的类型为 Foo 的引用，并将它分配给一个类型为 Foo 的新对象，并带有一个属性 "b".

Declaring a reference named b of type Foo and assign it to a new object of type Foo with an attribute "b".

Foo b = new Foo("b");