Java Vector lastIndexOf()
lastIndexOf() Java Vector类方法用于获取指定元素最后一次出现的索引在向量中。 Java lastIndexOf()方法有两种不同类型，可以根据其参数加以区分。这些是:
Java Vector lastIndexOf(Object o)方法
Java Vector lastIndexOf(Object o，int index)方法
lastIndexOf(Object o)方法:
它返回此向量中指定元素最后一次出现的索引。如果找不到该元素，则返回-1。
lastIndexOf(Object o，int index> c)方法:
此方法用于获取此向量中指定元素最后一次出现的索引。它开始从指定的索引向后搜索元素。如果找不到该元素，则返回-1。
语法
以下是
lastIndexOf()方法的声明:
public int lastIndexOf(Object obj)
public int lastIndexOf(Object obj, int index)
参数
| 参数 |
说明 |
必需/可选 |
| index |
这是一个索引，从该索引开始向后搜索元素。 |
必需 |
| obj |
它是要搜索的元素。 |
必需 |
返回
lastIndexOf()方法返回此向量中最后一次出现的指定元素的索引或返回-1如果向量不包含元素。
异常
IndexOutOfBoundsException -如果数组的索引为该方法，则抛出异常超出范围，即(index> = size())。
兼容版本
Java 1.2及更高版本
示例1
import java.util.*;
public class VectorLastIndexOfExample1 {
public static void main(String arg[]) {
//Create an empty Vector
Vector < Integer > in = new Vector < > ();
//Add elements in the vector
in.add(100);
in.add(200);
in.add(300);
in.add(100);
in.add(400);
//Obtain an index of last occurrence of the specified element
System.out.println("Index of element is: " +in.lastIndexOf(100));
}
}
输出:
示例2
import java.util.*;
public class VectorLastIndexOfExample2 {
public static void main(String arg[]) {
//Create an empty vector
Vector<String> vec = new Vector<>(4);
//Add elements in the vector
vec.add("Java");
vec.add("JavaScript");
vec.add("Android");
vec.add("Python");
//Obtain an index of the last occurrence of the specified element
System.out.println("Index of element is: " +vec.lastIndexOf("C"));
System.out.println("The element is not found.");
}
}
输出:
Index of element is: -1
The element is not found.
示例3
import java.util.*;
public class VectorLastIndexOfExample3 {
public static void main(String arg[]) {
//Create a first empty vector
Vector<String> vec = new Vector<>(4);
//Add elements in the first vector
vec.add("Facebook");
vec.add("Whatsapp");
vec.add("Twitter");
vec.add("Instagram");
vec.add("Skype");
//this would start searching of element in the backward direction from index -2
System.out.println("Index of element is found at: " +vec.lastIndexOf("Skype", 6));
}
}
输出:
Exception in thread "main" java.lang.IndexOutOfBoundsException: 6 >= 5
at java.base/java.util.Vector.lastIndexOf(Vector.java:469)
at myPackage.VectorLastIndexOfExample3.main(VectorLastIndexOfExample3.java:14)
示例4
import java.util.*;
public class VectorLastIndexOfExample4 {
public static void main(String arg[]) {
//Create an empty Vector
Vector < Integer > in = new Vector < > ();
//Add elements in the vector
in.add(101);
in.add(201);
in.add(301);
in.add(401);
in.add(501);
//this would start searching of element in the backward direction from index 3
System.out.println("Index of element is found at: " +in.lastIndexOf(201, 3));
}
}
输出:
Index of element is found at: 1
