常见应用场景：避免冗长的if-else或switch分支判断
解耦策略的定义、创建、使用三部分
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| 对不同大小文件进行排序
public class Sorter {
private static final long GB = 1000 * 1000 * 1000;
private static final List<AlgRange> algs = new ArrayList<>();
static {
algs.add(new AlgRange(0, 6*GB, SortAlgFactory.getSortAlg("QuickSort")));
algs.add(new AlgRange(6*GB, 10*GB, SortAlgFactory.getSortAlg("ExternalSort")));
algs.add(new AlgRange(10*GB, 100*GB, SortAlgFactory.getSortAlg("ConcurrentExternalSort")));
algs.add(new AlgRange(100*GB, Long.MAX_VALUE, SortAlgFactory.getSortAlg("MapReduceSort")));
}
public void sortFile(String filePath) {
// 省略校验逻辑
File file = new File(filePath);
long fileSize = file.length();
ISortAlg sortAlg = null;
for (AlgRange algRange : algs) {
if (algRange.inRange(fileSize)) {
sortAlg = algRange.getAlg();
break;
}
}
sortAlg.sort(filePath);
}
private static class AlgRange {
private long start;
private long end;
private ISortAlg alg;
public AlgRange(long start, long end, ISortAlg alg) {
this.start = start;
this.end = end;
this.alg = alg;
}
public ISortAlg getAlg() {
return alg;
}
public boolean inRange(long size) {
return size >= start && size < end;
}
}
}
|