Sorting an Array

1. 數字排序? int[] intArray = new int[] { 4, 1, 3, -23 };
Arrays.sort(intArray);
輸出： [-23, 1, 3, 4]
2. 字符串排序，先大寫后小寫 String[] strArray = new String[]{ "z", "a", "C" };
Arrays.sort(strArray);
輸出： [C, a, z]
3. 嚴格按字母表順序排序，也就是忽略大小寫排序 Case-insensitive sort
Arrays.sort(strArray, String.CASE_INSENSITIVE_ORDER);
輸出： [a, C, z]
4. 反向排序， Reverse-order sort
Arrays.sort(strArray, Collections.reverseOrder());
輸出：[z, a, C]
5. 忽略大小寫反向排序 Case-insensitive reverse-order sort
Arrays.sort(strArray, String.CASE_INSENSITIVE_ORDER);
Collections.reverse(Arrays.asList(strArray));
輸出： [z, C, a]

對于整數、字符串排序，jdk提供了默認的實現，如果要對一個對象數組排序，則要自己實現java.util.Comparator接口。

示例：

    import java.util.Arrays;
import java.util.Comparator;

class Cat {
	private String name;
	private float weight;
	
	public Cat(String name, float weight) {
		setName(name);
		setWeight(weight);
	}
	
	public Cat() {
	
	}
	
	public String getName() {
		return name;
	}
	
	public float getWeight() {
		return weight;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
	public void setWeight(float weight) {
		this.weight = weight;
	}
}

//創建一個比較器
class ByWeightComparator implements Comparator {
	public final int compare(Object c1, Object c2) {
		if(((Cat)c1).getWeight() > ((Cat)c2).getWeight()) {
			return 1;
		} else if(((Cat)c1).getWeight() == ((Cat)c2).getWeight()) {
					return 0;
		} else return -1;
	}
}

public class CatArrSortTest {
	public static void main(String[] args) {
		Cat c1 = new Cat("w", 100);
		Cat c2 = new Cat("d", 50);
		Cat c3 = new Cat("a", 80);
		Cat[] c = new Cat[]{c1, c2, c3};
		
		System.out.println("排序前:");
		for( Cat c4 : c) {
			System.out.print(c4.getName() + "," + c4.getWeight() + "\t");
		}

		Arrays.sort(c, new ByWeightComparator());

		System.out.println("\n排序后:");
		for( Cat c4 : c) {
			System.out.print(c4.getName() + "," + c4.getWeight() + "\t");
		}
	}
}

  

運行結果：

java數組排序Arrays.sort，以及結合Comparator接口的用法