이자바 13장(제네릭) 확인문제

Preface

 

대부분 기본적인 제네릭의 사용법과 관련된 문제들이므로 책의 내용만 잘 읽어봤다면 딱히 어려울 만한 문제는 없다.

---

 

- 2번

package ch13;

class Container<T> {
	private T t;

	public void set(T t) {
		this.t = t;
	}

	public T get() {
		return t;
	}
}

public class Exercise2 {

	public static void main(String[] args) {

		Container<String> container1 = new Container<String>();
		container1.set("홍길동");
		String str = container1.get();
		System.out.println(str);

		Container<Integer> container2 = new Container<Integer>();
		container2.set(6);
		int value = container2.get();
		System.out.println(value);
	}

}

 

 

- 3번

package ch13;

class Container1<T, M> {
	private T t;
	private M m;

	public void set(T t, M m) {
		this.t = t;
		this.m = m;
	}

	public T getKey() {
		return t;
	}

	public M getValue() {
		return m;
	}
}

public class Exercise3 {

	public static void main(String[] args) {

		Container1<String, String> container1 = new Container1<String, String>();
		container1.set("홍길동", "도적");
		String name1 = container1.getKey();
		String job = container1.getValue();
		System.out.println(name1 + " " + job);

		Container1<String, Integer> container2 = new Container1<String, Integer>();
		container2.set("홍길동", 35);
		String name2 = container2.getKey();
		int age = container2.getValue();
		System.out.println(name2 + " " + age);
	}

}

 

 

- 4번

package ch13;

class Pair2<K, V> {
	private K key;
	private V value;

	public Pair2(K key, V value) {
		this.key = key;
		this.value = value;
	}

	public K getKey() {
		return key;
	}

	public V getValue() {
		return value;
	}
}

class ChildPair<K, V> extends Pair2<K, V> {

	public ChildPair(K k, V v) {
		super(k, v);
	}
}

class OtherPair<K, V> {
	private K key;
	private V value;

	public OtherPair(K key, V value) {
		this.key = key;
		this.value = value;
	}

	public K getKey() {
		return key;
	}

	public V getValue() {
		return value;
	}
}

class Util3 {
	// 방법 1
    public static <K,V> V getValue(Pair2<K,V> p, K k) {
        if (p.getKey() == k) {
            return p.getValue();
        } else {
            return null;
        }
    }
    
//    방법 2
//    public static <P extends Pair<K,V>, K , V> V getValue(P p, K k) {
//    if (p.getKey() == k) {
//        return p.getValue();
//    } else {
//        return null;
//    }
}

public class Exercise4 {

	public static void main(String[] args) {

		Pair2<String, Integer> pair = new Pair2<>("홍길동", 35);
		Integer age = Util3.getValue(pair, "홍길동");
		System.out.println(age);

		ChildPair<String, Integer> childPair = new ChildPair<>("홍삼원", 20);
		Integer childAge = Util3.getValue(childPair, "홍삼순");
		System.out.println(childAge);

//		OtherPair<String , Integer> otherPair = new OtherPair<>("홍삼원", 20);
//		int otherAge = Util.getValue(otherPair, "홍삼원");
//		System.out.println(otherAge);
	}

}