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feat: utility method for padding list

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This commit is contained in:
easepan 2020-07-22 14:25:46 +08:00
parent d9f862ce67
commit 78729283e8
2 changed files with 20 additions and 25 deletions
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19
hutool-core/src/main/java/cn/hutool/core/collection/CollUtil.java
View File

@ -38,6 +38,7 @@ public class CollUtil {
/** /**
* 填充List，以达到最小长度 * 填充List，以达到最小长度
*
* @param list 列表 * @param list 列表
* @param minLen 最小长度 * @param minLen 最小长度
* @param padObj 填充的对象 * @param padObj 填充的对象
@ -45,32 +46,26 @@ public class CollUtil {
*/ */
public static <T> void padLeft(List<T> list, int minLen, T padObj) { public static <T> void padLeft(List<T> list, int minLen, T padObj) {
Objects.requireNonNull(list); Objects.requireNonNull(list);
if (isEmpty(list)) { if (list.isEmpty()) {
padRight(list, minLen, padObj); padRight(list, minLen, padObj);
return; return;
} }
int iterCnt = minLen - list.size(); for (int i = list.size(); i < minLen; i++) {
if (iterCnt < 1) { list.add(0, padObj);
return;
} }
List<T> padList = new ArrayList<>(iterCnt);
for (int i = 0; i < iterCnt; i++) {
padList.add(padObj);
}
list.addAll(0, padList);
} }
/** /**
* 填充List，以达到最小长度 * 填充List，以达到最小长度
*
* @param list 列表 * @param list 列表
* @param minLen 最小长度 * @param minLen 最小长度
* @param padObj 填充的对象 * @param padObj 填充的对象
* @param <T> 集合元素类型 * @param <T> 集合元素类型
*/ */
public static <T> void padRight(List<T> list, int minLen, T padObj) { public static <T> void padRight(Collection<T> list, int minLen, T padObj) {
Objects.requireNonNull(list); Objects.requireNonNull(list);
int iterCnt = minLen - list.size(); for (int i = list.size(); i < minLen; i++) {
for (int i = 0; i < iterCnt; i++) {
list.add(padObj); list.add(padObj);
} }
} }

26
hutool-core/src/test/java/cn/hutool/core/collection/CollUtilTest.java
View File

@ -21,28 +21,28 @@ public class CollUtilTest {
@Test @Test
public void testPadLeft() { public void testPadLeft() {
List<Integer> srcList = CollUtil.newArrayList(); List<String> srcList = CollUtil.newArrayList();
List<Integer> answerList = CollUtil.newArrayList(2, 1); List<String> answerList = CollUtil.newArrayList("a", "b");
CollUtil.padLeft(srcList, 1, 1); CollUtil.padLeft(srcList, 1, "b");
CollUtil.padLeft(srcList, 2, 2); CollUtil.padLeft(srcList, 2, "a");
Assert.assertEquals(srcList, answerList); Assert.assertEquals(srcList, answerList);
srcList = CollUtil.newArrayList(1, 2); srcList = CollUtil.newArrayList("a", "b");
answerList = CollUtil.newArrayList(1, 2); answerList = CollUtil.newArrayList("a", "b");
CollUtil.padLeft(srcList, 2, 1); CollUtil.padLeft(srcList, 2, "a");
Assert.assertEquals(srcList, answerList); Assert.assertEquals(srcList, answerList);
srcList = CollUtil.newArrayList(3); srcList = CollUtil.newArrayList("c");
answerList = CollUtil.newArrayList(1, 1, 3); answerList = CollUtil.newArrayList("a", "a", "c");
CollUtil.padLeft(srcList, 3, 1); CollUtil.padLeft(srcList, 3, "a");
Assert.assertEquals(srcList, answerList); Assert.assertEquals(srcList, answerList);
} }
@Test @Test
public void testPadRight() { public void testPadRight() {
List<Integer> srcList = CollUtil.newArrayList(6); List<String> srcList = CollUtil.newArrayList("a");
List<Integer> answerList = CollUtil.newArrayList(6, 3, 3, 3, 3); List<String> answerList = CollUtil.newArrayList("a", "b", "b", "b", "b");
CollUtil.padRight(srcList, 5, 3); CollUtil.padRight(srcList, 5, "b");
Assert.assertEquals(srcList, answerList); Assert.assertEquals(srcList, answerList);
} }