[英]“+” operator for Java-classes
I have a class like this: 我有一个这样的课:
private static class Num {
private int val;
public Num(int val) {
this.val = val;
}
}
Is it possible to add to objects of the class by using the "+"-operator? 是否可以使用“+” - 运算符添加到类的对象?
Num a = new Num(18);
Num b = new Num(26);
Num c = a + b;
No, you can't. 不,你不能。 +
is overloaded only for numbers, chars and String
, and you are not allowed to define any additional overloadings. +
仅为数字,字符和String
重载,并且不允许定义任何其他重载。
There is one special case, when you can concatenate any objects' string representation - if there is a String
object in the first two operands, toString()
is called on all other objects. 有一种特殊情况,当你可以连接任何对象的字符串表示时 - 如果前两个操作数中有一个String
对象,则在所有其他对象上调用toString()
。
Here's an illustration: 这是一个例子:
int i = 0;
String s = "s";
Object o = new Object();
Foo foo = new Foo();
int r = i + i; // allowed
char c = 'c' + 'c'; // allowed
String s2 = s + s; // allowed
Object o2 = o + o; // NOT allowed
Foo foo = foo + foo; // NOT allowed
String s3 = s + o; // allowed, invokes o.toString() and uses StringBuilder
String s4 = s + o + foo; // allowed
String s5 = o + foo; // NOT allowed - there's no string operand
No, because James Gosling said so: 不,因为詹姆斯·高斯林这么说:
I left out operator overloading as a fairly personal choice because I had seen too many people abuse it in C++. 我遗漏了操作符重载作为一个相当个人的选择,因为我看到有太多人在C ++中滥用它。
Source: http://www.gotw.ca/publications/c_family_interview.htm 资料来源: http : //www.gotw.ca/publications/c_family_interview.htm
Reference: Why doesn't Java offer operator overloading? 参考: 为什么Java不提供运算符重载?
不.Java不支持运算符重载(对于用户定义的类)。
There is no operators overloading in java. java中没有运算符重载。 The only thing which is supported for objects, is string concatenations via "+". 唯一支持对象的是通过“+”进行字符串连接。 If you have a sequences of objects joined via "+" and at least one of them is a String, then the result will be inlined to String creation. 如果您有一系列通过“+”连接的对象,并且其中至少有一个是String,则结果将内联到String创建。 Example: 例:
Integer a = 5;
Object b = new Object();
String str = "Test" + a + b;
will be inlined to 将被内联
String str = new StringBuilder("Test").append(a).append(b).toString();
不,这是不可能的,因为Java不支持运算符重载 。
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