敲代碼之泛型學習

1、一個簡單的泛型案例

package test;

public class PairTest2 {
	public static void main(String[] args){
		String[] words = {"Mary","had","a","little","lamb"};
		Pair<String> mm = ArrayAlg.minmax(words);
		System.out.println("min = " + mm.getFirst());
		System.out.println("max = " + mm.getSecond());
				
	}

}

class ArrayAlg{
	public static Pair<String> minmax(String[] a){
		if(a == null || a.length == 0) return null;
		String min = a[0];
		String max = a[0];
		for (int i = 0; i < a.length; i++) {
			if(min.compareTo(a[i]) > 0) min = a[i];
			if(max.compareTo(a[i]) < 0) max = a[i];
		}
		return new Pair<>(min, max);
	}
}

class Pair<T> {
	private T first;
	private T second;
	
	public Pair(){first = null; second = null;}
	public Pair(T first, T second){this.first = first; this.second = second;}
	
	public T getFirst(){return first;}
	public T getSecond(){return second;}

	public void setFirst(T newValue){first = newValue;}
	public void setSecond(T newValue){second = newValue;}
	
}

class Pair1<HS> {
	private HS first;
	private HS second;
	
	public Pair1(){first = null; second = null;}
	public Pair1(HS first, HS second){this.first = first; this.second = second;}
	
	public HS getFirst(){return first;}
	public HS getSecond(){return second;}

	public void setFirst(HS newValue){first = newValue;}
	public void setSecond(HS newValue){second = newValue;}
	
}

說明：使用<T>來聲明一個類型持有者名稱，然後就可以把T當作一個類型代表來聲明成員、參數和返回值類型。