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What is method overloading?
Method overloading is a means of handling different data types in a unified way.
How to constitute method overloading?
The method names are the same but the formal parameters are different. The difference in formal parameters is expressed in: 1). The number of formal parameters is different 2). The types of formal parameters are different 3). The order of formal parameters is different
Notes
1. If the return values of the two methods are different, but everything else is the same. This does not constitute method overloading. An error will be reported during compilation:
Sample code (wrong): Test.java
/*返回值的不同并不能构成方法的重载*/ public class Test { public static void main(String[] args) { } } class A { public void f() { //返回值为 void } public int f() { //返回值为 int, 其他和上面的f()方法是一样的 return 1; } }
Error message:
Test.java:12: error: method f() is already defined in class A public int f() { ^ 1 error 2. 构造方法和普通方法一样, 也可以方法重载。
Sample code (correct): Test.java
/* 方法的重载 * 输出结果: * public A() {} 这个构造方法被调用了 * public A(int i) {} 这个构造方法被调用了 * public void f() {} 这个构造方法被调用了 * public void f(int i) {} 这个构造方法被调用了 */ public class Test { public static void main(String[] args) { A aa1 = new A(); //调用9行那个方法 A aa2 = new A(1); //调用13行那个方法 aa1.f(); //调用17行那个方法 aa2.f(1); //调用21行那个方法 } } class A { public A() { //9行 System.out.printf("public A() {} 这个构造方法被调用了\n"); } public A(int i) { //13行 System.out.printf("public A(int i) {} 这个构造方法被调用了\n"); } public void f() { //17行 System.out.printf("public void f() {} 这个构造方法被调用了\n"); } public void f(int i) { //21行 System.out.printf("public void f(int i) {} 这个构造方法被调用了\n"); } }
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