125_容器_內置類比較_Comparator_排序工具類實現

• ComparatorImpl

package collection.sort.comparator;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class ComparatorImpl {
    public static void main(String[] args) {
        System.out.println("==========使用Comparator排序數組===============");
        String[] arr2 ={"a","abcd","abc","def"};
        arr2 =new String[]{"a","abcd","abc","def"};
        CompareUtils.sort(arr2,new StringCompare());
        System.out.println(Arrays.toString(arr2));

        System.out.println("==========使用Comparator排序List===========");
        //存放容器中
        List<String> list =new ArrayList<String>();
        list =new ArrayList<String>();
        list.add("a");
        list.add("abcd");
        list.add("abc");
        list.add("def");
        CompareUtils.sort(list,new StringCompare());
        System.out.println(list);   
    }
}

• CompareUtils

package collection.sort.comparator;

import java.util.Comparator;
import java.util.List;

public class CompareUtils {

    /**
     * 數組的排序 (降序+Comparator接口)
     * @param arr
     */
    @SuppressWarnings("unchecked")
    public static <T> void sort(Object[] arr,Comparator<T> com){
        //從大到小排序降序
        boolean sorted= true;
        int len =arr.length;
        for(int j=0;j<len-1;j++){ //趟數
            sorted =true; //假定有序
            for(int i=0;i<len-1-j;i++){ //次數
                if(com.compare((T)arr[i], (T)arr[i+1])<0){
                    Object temp = arr[i];
                    arr[i] =arr[i+1];
                    arr[i+1] =temp;
                    sorted =false; //假定失敗
                }
            }
            if(sorted){ //減少趟數
                break;
            }
        }
    }
    /**
     * List的排序(降序+Comparator接口)
     * @param list
     * @param com
     */
    @SuppressWarnings("unchecked")
    public static  <T> void sort(List<T> list,Comparator<T> com){
        //第一步:轉成數組
        Object[] arr =list.toArray();
        sort(arr,com);
        //第二步:改變容器中對應的值
        for(int i=0;i<arr.length;i++){
            list.set(i, (T)(arr[i]));
        }
    }
}

• StringCompare

package collection.sort.comparator;

import java.util.Comparator;
/**
 * String排序規則的業務類
 * @author zhushen
 *
 */
public class StringCompare implements Comparator<String>{
    /**按String的長度來比較大小
     *1.正數:o1>o2
     *2.負數:o1<o2
     *3.0:o1=o2
     */
    @Override
    public int compare(String o1, String o2) {
        return o1.length()-o2.length();
    }

}