Detailed explanation of how to use variable parameters in Java

Detailed explanation of how to use variable parameters in Java

In Java, variable parameters are a special syntax that allows us to define a method that when called Any number of parameters can be passed in. This syntax greatly simplifies code writing and calling flexibility. This article will introduce in detail the use of variable parameters in Java, and attach specific code examples.

1. Definition of variable parameters

Variable parameters in Java are implemented by adding ellipses (...) to method parameters. The ellipses indicate that any number of parameters can be accepted. For example:

public void printNames(String... names) {
//Method body
}

In the above code, the parameter names of the printNames method are variable parameter. We can pass in any number of String type parameters.

2. Use of variable parameters

Variable parameters are treated as an array inside the method. We can access the elements of the variadic parameters just like we do with arrays. For example:

public void printNames(String... names) {
for (String name : names) {

  System.out.println(name);

}
}

In the above In the code, a for-each loop is used to traverse the variable parameter names and print the value of each element in turn.

3. Calling the variable parameter method

When calling the variable parameter method, we can pass in any number of parameters, or even no parameters. For example:

printNames("Alice", "Bob", "Charlie"); // Pass in 3 parameters
printNames("David"); // Pass in 1 parameter
printNames(); // No parameters are passed in, the length of the names array is 0

In the above code, we call the printNames method with different numbers of parameters. The flexibility of variable parameters makes the method call very convenient. .

4. Combined use of variable parameters and ordinary parameters

In the parameter list of a method, variable parameters must be placed last. We can also use variadic parameters with normal parameters. For example:

public void calculateSum(int initial, int... numbers) {
int sum = initial;
for (int number : numbers) {

  sum += number;

}
System.out.println("Sum: " sum);
}

In the above code, the calculateSum method accepts an initial value initial and any number of int type parameters. We can calculate their sum by passing in different numbers of parameters.

5. Variable parameters and method overloading

When a method is overloaded, the method with variable parameters will be considered the last choice. For example:

public void printNames(String... names) {
System.out.println("Printing names: ");
for (String name : names) {

  System.out.println(name);

}
}

public void printNames(String name) {
System.out.println("Printing name: " name);
}

at In the above code, the printNames method with the same name accepts variable parameters and a single parameter respectively. When calling the printNames method, if multiple parameters are passed in, the variable parameter method will be selected.

Summary:

This article introduces in detail the use of variable parameters in Java. By using variadic parameters, we can define more flexible methods that accept any number of parameters. Inside the method, the variadic parameters are used as an array. In addition, we also introduced the combination of variable parameters and ordinary parameters and the selection rules when overloading methods. I hope this article helps you better understand and use variadic parameters in Java.

Sample code:

public class Main {
public static void main(String[] args) {

  Main main = new Main();
  main.printNames("Alice", "Bob", "Charlie"); // 传入3个参数
  main.printNames("David"); // 传入1个参数
  main.printNames(); // 不传入参数，names数组长度为0
  
  main.calculateSum(10, 1, 2, 3); // 传入多个参数
  main.calculateSum(10, 5); // 传入1个参数
  main.calculateSum(10); // 不传入参数

}

public void printNames (String... names) {

  for (String name : names) {
     System.out.println(name);
  }

}

public void calculateSum(int initial, int... numbers) {

  int sum = initial;
  for (int number : numbers) {
     sum += number;
  }
  System.out.println("Sum: " + sum);

}
}

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