# 使用索引在 Java 中搜索元素 > 原文： [https://beginnersbook.com/2014/06/search-elements-in-vector-using-index-java-example/](https://beginnersbook.com/2014/06/search-elements-in-vector-using-index-java-example/) 在本教程中，我们将学习以下四种使用索引值在`Vector`中搜索元素的方法。 1）`public int indexOf(Object o)`：返回`Vector`中第一次出现的对象`o`的索引。 2）`public int indexOf(Object o, int startIndex)`：返回此向量中第一次出现的对象`o`的索引，从`startIndex`（包括）开始向前搜索。 3）`public int lastIndexOf(Object o)`：返回`Vector`中最后一次出现的对象`o`的索引。 4）`public int lastIndexOf(Object o, int startIndex)`：它返回此向量中最后一次出现的指定元素的索引，从`startIndex`（包括）向后搜索。 #### 示例 在这个例子中，我们使用了上面提到的所有四种方法来证明它们的工作原理。 ```java import java.util.Vector; public class SearchVector { public static void main(String[] args) { // Create a Vector object Vector<String> vector = new Vector<String>(); //Add elements to Vector vector.add("Kate"); vector.add("Patt"); vector.add("Kluge"); vector.add("Karon"); vector.add("Patt"); vector.add("Monica"); vector.add("Patt"); //This would return the index of first occurrence int first_index = vector.indexOf("Patt"); System.out.println("First Occurrence of Patt at index: "+first_index); //This would return the index of last occurrence int last_index = vector.lastIndexOf("Patt"); System.out.println("Last Occurrence of Patt at index: "+last_index); //This would start search from index 2(inclusive) int after_index = vector.indexOf("Patt", 2); System.out.println("Occurrence after index 2: "+after_index); //This would search the element backward starting from index 6(inclusive) int before_index = vector.lastIndexOf("Patt", 6); System.out.println("Occurrence before index 6: "+before_index); } } ``` **输出：** ```java First Occurrence of Patt at index: 1 Last Occurrence of Patt at index: 6 Occurrence after index 2: 4 Occurrence before index 6: 6 ``` **参考** [`Vector` javadoc](https://docs.oracle.com/javase/7/docs/api/java/util/Vector.html "javadoc")