[파워자바] 22장 프로그래밍 솔루션 답지

 

1.

import java.util.*;
public class RandomList<T> {
	Random r = new Random();
	String[] sample = {"i", "walk", "the", "line"};
	List<T> list = (List<T>) Arrays.asList(sample);
	public void add(T item){
		list.add(item);
	}
	public T select() {
		int num = r.nextInt(list.size());
		return list.get(num);
	}
}

 

2.

class MyMath<T extends Number> {
	double v=0.0;
	public double getAverage(T[] a){
		for (int i = 0; i < a.length; i++)
			v = v + a[i].doubleValue();
		return v/a.length;
	}
}

public class Test
{
	public static void main(String[] args) {
		Integer[] list = { 1, 2, 3, 4, 5, 6 };
		
		MyMath<Integer> m = new MyMath<Integer>();
		System.out.println(m.getAverage(list));
	}
}

 

 

3.

class MyPair<T> {
	private T str1, str2;
	public MyPair(T s1, T s2){
		str1 = s1;
		str2 = s2;
	}
	public void getStr1(T s1){
		str1 = s1;
	}
	public void getStr2(T s2){
		str2 = s2;
	}
	public T setStr1(){
		return str1;
	}
	public T setStr2(){
		return str2;
	}
	public String toString(){
		return "str1 : " + str1 + " str2 : " + str2;
	}	
}
public class MyPairTest{
	public static void main(String[] args){
		MyPair<String> fruit = new MyPair<String>("사과", "포도");
		System.out.println(fruit.toString());
	}
}

 

4.

public class Test
{
	public static <T> void displayArray(T a)
	{
			System.out.println(a.getClass().getName());
	}
	public static void main(String[] args) {
		int x=0;
		float y=0.0F;
		Test.<Object>displayArray(x);
		Test.<Object>displayArray(y);
	}
}

 

5.

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;

public class Test
{
	public static void main(String[] args) {
		ArrayList<Double> list = new ArrayList<Double>();
		Scanner sc = new Scanner(System.in);
		
		for(int i=0;i<10; i++){
			System.out.print("심사위원의 점수: ");
			double value = sc.nextDouble();
			list.add(value);
		}
		
		double max = Collections.max(list);
		double min = Collections.min(list);
		double sum = 0.0;
		double value = 0.0;
		for(int i=0;i<10; i++){
			value = list.get(i);
			if( value != min && value != max )
				sum += value;
		}
		System.out.print("점수의 합: "+ sum);
	}
}

 

6.

import java.util.ArrayList;
import java.util.Collections;
import java.util.Scanner;


class Student implements Comparable<Student>
{
	public Student(String name, String address, String phone) {
		super();
		this.name = name;
		this.address = address;
		this.phone = phone;
	}
    public int compareTo(Student s) {
        return name.compareTo(s.name);
    }
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAddress() {
		return address;
	}
	public void setAddress(String address) {
		this.address = address;
	}
	public String getPhone() {
		return phone;
	}
	public void setPhone(String phone) {
		this.phone = phone;
	}
	@Override
	public String toString() {
		return "Student [name=" + name + ", address=" + address + ", phone="
				+ phone + "]";
	}
	String name;
	String address;
	String phone;
}
public class Test
{
	public static void main(String[] args) {
		ArrayList<Student> list = new ArrayList<Student>();
		Scanner sc = new Scanner(System.in);
		
		for(int i=0;i<10; i++){
			list.add(new Student("name"+i, "address"+i, "phone"+i));
		}
		
		Collections.sort(list);
		int pos = Collections.binarySearch(list, new Student("name3", "address3", "phone3"));
		System.out.println(pos);
	}
}

 

7.

import java.util.HashSet;

public class Lotto {
	@Override
	public String toString() {
		return "Lotto [set=" + set + "]";
	}

	HashSet<Integer> set = new HashSet<Integer>();

	public Lotto() {
		int d;
		for (int i = 0; i < 6; i++) {
			do {
				d = (int) (Math.random() * 44.0 + 1.0);
			} while (set.contains(d));
			set.add(d);
		}
	}

	public static void main(String[] args) {
		Lotto lotto = new Lotto();
		System.out.println(lotto);

	}

}