Java判断字符串是否在List中的方案详解(忽略大小写)

import java.util.*;
public class CaseInsensitiveLookup {
    private final Set<String> lowerCaseSet;
    public CaseInsensitiveLookup(List<String> originalList) {
        // 预处理：将所有字符串转为小写并存入HashSet
        this.lowerCaseSet = new HashSet<>(originalList.size());
        for (String s : originalList) {
            lowerCaseSet.add(s.toLowerCase());
        }
    }
    public boolean containsIgnoreCase(String target) {
        return lowerCaseSet.contains(target.toLowerCase());
    }
}

import java.util.*;
public class CaseInsensitiveLookup {
    private final Set<String> treeSet;
    public CaseInsensitiveLookup(List<String> originalList) {
        this.treeSet = new TreeSet<>(String.CASE_INSENSITIVE_ORDER);
        treeSet.addAll(originalList);
    }
    public boolean containsIgnoreCase(String target) {
        return treeSet.contains(target);
    }
}

import java.util.*;
public class CaseInsensitiveLookup {
    private final List<String> originalList;
    public CaseInsensitiveLookup(List<String> originalList) {
        this.originalList = originalList;
    }
    public boolean containsIgnoreCase(String target) {
        return originalList.parallelStream()
            .anyMatch(s -> s.equalsIgnoreCase(target));
    }
}

List<String> largeList = Arrays.asList("Apple", "Banana", "Orange", ...);
CaseInsensitiveLookup lookup = new CaseInsensitiveLookup(largeList);
// 频繁调用
boolean contains = lookup.containsIgnoreCase("apple");  // 返回true