用正则表达式匹配字符串数组内容 java

Question

我是 java 的新手。我正在尝试使用 java 正则表达式来比较两个包含名称的字符串数组，然后使用嵌套的 for 循环打印出匹配的名称和不匹配的名称。下面是我的代码

public class Main {

    public static void main(String[] args) {

    // write your code here
        String regex;
        Pattern pattern;
        String stringToBeMatched;
        Matcher matcher;
        boolean b;
     String [] names1 = {"Peter","Harry","Potter","Mary","Jerry"};
        String [] names2 = {"Adam","Jerry","Potter","Martin","Chris", "Rose"};
        //try a loop with two variables for loop

                for (int x=0;x >= names2.length;x++) {
                     regex = names2[x];
                     pattern = Pattern.compile(regex);

                    for(int y = 0; y >= names1.length; y++){
                        stringToBeMatched = names1[y];
                        matcher = pattern.matcher(stringToBeMatched);
                        b = matcher.find();

                        if (b) {System.out.println(names1[y] +" has a match");}
                        else{System.out.println(names1[y] +" has no match");}
                    }
                }
    }
}

代码执行并 returns 输出 Process finished with exit code 0 而不显示任何 System.out.println() 语句指定的任何消息。伙计们，我做错了什么？

Answer 1

除非我误解了你的意图，否则你不应该在这里使用正则表达式。我的理解是您想比较两个数组的重复元素。

你有你的阵列：

String[] names1 = {"Peter", "Harry", "Potter", "Mary", "Jerry"};
String[] names2 = {"Adam", "Jerry", "Potter", "Martin", "Chris", "Rose"};

方法 1 - 嵌套 for 循环。

for(int i = 0; i < names1.length; i++) {
  for(int j = 0; j < names2.length; j++) {
    if(names1[i].equals(names2[j])) System.out.println(names1[i] + " is in both arrays.");
  }
}

方法 2 - 嵌套的 foreach 循环。

for(String name1 : names1) {
  for(String name2 : names2) {
    if(name1.equals(name2)) System.out.println(name1 + " is in both arrays.");
  }
}

方法 3 - 使用 List.

List<String> names2List = Arrays.asList(names2);

for(String name1 : names1) {
  if(names2List.contains(name1)) System.out.println(name1 + " is in both arrays.");
}

方法 4 - 使用 Set. This works because HashSet#add() 不会添加重复项，如果需要，returns false。

Set<String> names2Set = new HashSet<>(Arrays.asList(names2));

for(String name1 : names1) {
  if(!names2Set.add(name1)) System.out.println(name1 + " is in both arrays.");
}

方法 5 - 使用 Streams。如果你想变得花哨。

for(String name1 : names1) {
  if(Arrays.stream(names2).anyMatch(name1::equals)) System.out.println(name1 + " is in both arrays.");
}

Answer 2

对于 lambda 函数，使用 "distinct" 不打印重复值。

        String [] names1 = {"Peter","Harry","Potter","Mary","Jerry"};
        String [] names2 = {"Adam","Jerry","Potter","Martin","Chris", "Rose", "Peter", "Peter"};
        for (String name1:
             names1) {
            Arrays.stream(names2).filter(name1::equals).distinct().forEach(System.out::println);
    }

用正则表达式匹配字符串数组内容 java

matching string array content with regular expression java

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string-matching

nested-loops