关于 Java Collections API 您不知道事2

import java.util.*;

public class OrderAndPosition
{
public static <T> void dumpArray(T[] array)
{
System.out.println("=============");
for (int i=0; i<array.length; i++)
System.out.println("Position " + i + ": " + array[i]);
}
public static <T> void dumpList(List<T> list)
{
System.out.println("=============");
for (int i=0; i<list.size(); i++)
System.out.println("Ordinal " + i + ": " + list.get(i));
}

public static void main(String[] args)
{
List<String> argList = new ArrayList<String>(Arrays.asList(args));

dumpArray(args);
args[1] = null;
dumpArray(args);

dumpList(argList);
argList.remove(1);
dumpList(argList);
}
}

// FileUtils.java
import java.io.*;
import java.util.*;

public class FileUtils
{
public static Iterable<String> readlines(String filename)
throws IOException
{
final FileReader fr = new FileReader(filename);
final BufferedReader br = new BufferedReader(fr);

return new Iterable<String>() {
public <code>Iterator</code><String> iterator() {
return new <code>Iterator</code><String>() {
public boolean hasNext() {
return line != null;
}
public String next() {
String retval = line;
line = getLine();
return retval;
}
public void remove() {
throw new UnsupportedOperationException();
}
String getLine() {
String line = null;
try {
line = br.readLine();
}
catch (IOException ioEx) {
line = null;
}
return line;
}
String line = getLine();
};
}
};
}
}

//DumpApp.java
import java.util.*;

public class DumpApp
{
public static void main(String[] args)
throws Exception
{
for (String line : FileUtils.readlines(args[0]))
System.out.println(line);
}
}

// Person.java
import java.util.*;

public class Person
implements Iterable<Person>
{
public Person(String fn, String ln, int a, Person... kids)
{
this.firstName = fn; this.lastName = ln; this.age = a;
for (Person kid : kids)
children.add(kid);
}

// ...

public void setFirstName(String value) { this.firstName = value; }
public void setLastName(String value) { this.lastName = value; }
public void setAge(int value) { this.age = value; }

public int hashCode() {
return firstName.hashCode() & lastName.hashCode() & age;
}

// ...

private String firstName;
private String lastName;
private int age;
private List<Person> children = new ArrayList<Person>();
}

// MissingHash.java
import java.util.*;

public class MissingHash
{
public static void main(String[] args)
{
Person p1 = new Person("Ted", "Neward", 39);
Person p2 = new Person("Charlotte", "Neward", 38);
System.out.println(p1.hashCode());

Map<Person, Person> map = new HashMap<Person, Person>();
map.put(p1, p2);

p1.setLastName("Finkelstein");
System.out.println(p1.hashCode());

System.out.println(map.get(p1));
}
}

import java.util.*;

public class UsingSortedSet
{
public static void main(String[] args)
{List<Person> persons = Arrays.asList(
new Person("Ted", "Neward", 39),
new Person("Ron", "Reynolds", 39),
new Person("Charlotte", "Neward", 38),
new Person("Matthew", "McCullough", 18)
);
SortedSet ss = new TreeSet(new Comparator<Person>() {
public int compare(Person lhs, Person rhs) {
return lhs.getLastName().compareTo(rhs.getLastName());
}
});
ss.addAll(perons);
System.out.println(ss);
}
}