Question

Could someone please explain what the for loop in this class does? Specifically the part with (String person : people)

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);

    }
}
}

Thank you.

Answer 1

It’s called the foreach syntax. It works with arrays and Objects that implement Iterable.

For arrays (as here) it’s equivalent to this code:

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

For Iterable<T> iterable (eg a List), it’s equivalent to:

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

This code pattern was so common, and added so little value, this abbreviated form of looping was officially made part of the java language in version 1.5 (aka “Java 5”).