Java:解释这个 for() 循环参数的作用

Question

谁能解释一下这个类中的 for 循环是做什么的？特别是带有 (String person : people) 的部分

import java.util.Scanner;

/**
 * This program uses the startsWith method to search using
 * a partial string
 * 
 *
 */
public class PersonSearch {

public static void main(String[] args){
    String lookUp;  //To hold a lookup string

    //Create an array of names
    String[] people= {"Cutshaw, Will", "Davis, George",
            "Davis, Jenny", "Russert, Phil", 
            "Russel, Cindy", "Setzer, Charles",
            "Smathers, Holly", "Smith, Chris", 
            "Smith, Brad", "Williams, Jean" };

    //Create a Scanner object for keyboard input
    Scanner keyboard=new Scanner(System.in);

    //Get a partial name to search for
    System.out.println("Enter the first few characters of "+
            "the last name to look up: ");
    lookUp=keyboard.nextLine();

    //Display all of the names that begin with the
    //string entered by the user
    System.out.println("Here are the names that match:");
    for(String person : people){
        if (person.startsWith(lookUp))
            System.out.println(person);

    }
}
}

谢谢。

Answer 1

它叫做 foreach句法。它适用于实现 Iterable 的数组和对象.

对于数组(如此处)，它等同于此代码:

for (int i = 0; i < people.length; i++) {
    person = people[i];
    // code inside loop
}

对于 Iterable<T> iterable (例如一个列表)，它等同于:

for (Iterator<T> i = iterable.iterator(); i.hasNext(); ) {
    T next = i.next();
    // code inside loop
}

这种代码模式非常普遍，并且增加的值(value)很少，这种循环的缩写形式在 1.5 版(也称为“Java 5”)中正式成为 java 语言的一部分。