Java Collections indexOfSubList()用法及代码示例

java.util.Collections类的indexOfSubList()方法用于返回指定源列表中指定目标列表第一次出现的起始位置，如果没有出现，则返回-1。更正式地，返回最低索引i，以使source.subList(i，i + target.size()).equals(target)或-1(如果没有这样的索引)。 (如果target.size()> source.size()，则返回-1。)

此实现使用“brute force”技术扫描源列表，依次在每个位置查找与目标的匹配项。

用法:

public static int indexOfSubList(List source, List target)

参数：该方法将以下参数作为参数

• source –在其中搜索首次出现的目标的列表。
• target –要搜索的列表作为源的子列表。

返回值：此方法返回指定源列表中指定目标列表第一次出现的起始位置，如果没有出现，则返回-1。

以下示例说明了indexOfSubList()方法

示例1:

// Java program to demonstrate 
// indexOfSubList() method 
// for String value 
  
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) 
        throws Exception 
    { 
        try { 
  
            // creating object of List<String> 
            List<String> arrlistsrc = new ArrayList<String>(); 
            List<String> arrlisttarget = new ArrayList<String>(); 
  
            // Adding element to arrlistsrc 
            arrlistsrc.add("A"); 
            arrlistsrc.add("B"); 
            arrlistsrc.add("C"); 
            arrlistsrc.add("D"); 
            arrlistsrc.add("E"); 
  
            // Adding element to arrlisttarget 
            arrlisttarget.add("C"); 
            arrlisttarget.add("D"); 
            arrlisttarget.add("E"); 
  
            // print the source list 
            System.out.println("Source list: " + arrlistsrc); 
  
            // print the target list 
            System.out.println("Target list: " + arrlisttarget); 
  
            // check target list in source list 
            int index = Collections 
                            .indexOfSubList(arrlistsrc, 
                                            arrlisttarget); 
  
            // print the index 
            System.out.println("Target list starts at index: "
                               + index); 
        } 
  
        catch (IllegalArgumentException e) { 
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

输出：

Source list: [A, B, C, D, E]
Target list: [C, D, E]
Target list starts at index: 2

示例2:

// Java program to demonstrate 
// indexOfSubList() method 
// for Integer value 
  
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) 
        throws Exception 
    { 
        try { 
  
            // creating object of List<Integer> 
            List<Integer> arrlistsrc = new ArrayList<Integer>(); 
            List<Integer> arrlisttarget = new ArrayList<Integer>(); 
  
            // Adding element to arrlistsrc 
            arrlistsrc.add(20); 
            arrlistsrc.add(30); 
            arrlistsrc.add(40); 
            arrlistsrc.add(50); 
            arrlistsrc.add(60); 
  
            // Adding element to arrlisttarget 
            arrlisttarget.add(40); 
            arrlisttarget.add(50); 
  
            // print the source list 
            System.out.println("Source list: " + arrlistsrc); 
  
            // print the target list 
            System.out.println("Target list: " + arrlisttarget); 
  
            // check target list in source list 
            int index = Collections 
                            .indexOfSubList(arrlistsrc, 
                                            arrlisttarget); 
  
            // print the index 
            System.out.println("Target list starts at index: "
                               + index); 
        } 
  
        catch (IllegalArgumentException e) { 
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

输出：

Source list: [20, 30, 40, 50, 60]
Target list: [40, 50]
Target list starts at index: 2