How does the Java function overloading mechanism perform type checking at compile time?

Java function overloading resolves function calls through compile-time type checking: Comparing parameter types: The compiler compares the actual parameters with the formal parameters in the overloaded function. Find the best matching function: The compiler looks for the function with the fewest type conversions or casts. Return the matching function: If a unique match is found, return the function; otherwise, a compilation error will be reported.

Compile-time type checking of Java function overloading mechanism

Preface

Function overloading allows the creation of multiple functions in the same class with the same name but different parameter lists. The Java compiler resolves function overloading by checking the function's parameter types.

Compile-time type checking

When the compiler encounters a function call, it performs the following steps:

1. Compare parameter types: The compiler compares the actual parameters in the function call with the formal parameters in the overloaded function.
2. Find the best matching function: The compiler looks for the function with the best matching argument type. The best match is the function with the fewest type conversions or casts.
3. Return matching functions: If a unique matching function is found, the compiler returns that function. Otherwise, a compilation error will be reported.

Practical case

Consider the following Java class with overloaded functions:

public class Fun {
    public void print(int num) {
        System.out.println("Printing int: " + num);
    }

    public void print(String str) {
        System.out.println("Printing string: " + str);
    }
}

Example:

Fun obj = new Fun();
obj.print(10); // 调用第一个 print() 方法
obj.print("Hello"); // 调用第二个 print() 方法

Compile time checking process:

1. For print(10):

   • Parameters The type is int.
   • This matches the first print() method, and the parameter type is also int.

2. For print("Hello"):

   • The parameter type is String.
   • This matches the second print() method with parameter type String.

#The compiler successfully parses function calls at compile time because each call has the argument type that best matches the overloaded method.

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