如何检查arraylist是否包含字符串

Question

我有这个代码,找到女性艺术家,男性艺术家或乐队的数量 -

 import java.util.*;


 public class FindGender {


    public static void main(String[] args) {
        // TODO code application logic here
        ArrayList < String > artists = new ArrayList < > ();
        int mnum = 0, fnum = 0, bnum = 0;
        artists.add("Beyonce (f)");
        artists.add("Drake (m)");
        artists.add("Madonna (f)");
        artists.add("Michael Jackson (m)");
        artists.add("Porcupine Tree (b)");
        artists.add("Opeth (b)");
        artists.add("FallOut Boy (b)");
        artists.add("Rick Ross {m}");
        artists.add("Chris Brown (m)");
        if (artists.contains("(b)")) bnum++;
        if (artists.contains("(m)")) mnum++;
        if (artists.contains("(f)")) fnum++;
        System.out.println("The number of male artists is: " + mnum);
        System.out.println("The number of female artists is: " + fnum);
        System.out.println("The number of bands is: " + bnum);
    }

 }

但输出显示 - 运行:

The number of male artists is: 0
The number of female artists is: 0
The number of bands is: 0
BUILD SUCCESSFUL (total time: 0 seconds)

任何帮助,将不胜感激

Answer 1

list#contains()比较列表中的整个字符串而不是字符串的一部分，你可以这样做

if(artists.stream().anyMatch(e -> e.contains("(b)")))   // java 8 solution

即迭代列表并检查列表元素的包含情况。

Answer 2

包含和包含String的一部分是不同的.为了返回true,它应该匹配整个String.

这有效

for (String item : artists) {
        if (item.contains("(b)")) bnum++;
        if (item.contains("(m)")) mnum++;
        if (item.contains("(f)")) fnum++;    
}

Answer 3

你可以使用类似的东西if(string.indexOf("(f)")!=-1) fnum++。这在您的代码中看起来像这样。

public static void main(String[] args) 
{
    // TODO code application logic here
    ArrayList<String> artists = new ArrayList<>();
    int mnum = 0, fnum = 0, bnum = 0;
    artists.add("Beyonce (f)");
    artists.add("Drake (m)");
    artists.add("Madonna (f)");
    artists.add("Michael Jackson (m)");
    artists.add("Porcupine Tree (b)");
    artists.add("Opeth (b)");
    artists.add("FallOut Boy (b)");
    artists.add("Rick Ross (m)");
    artists.add("Chris Brown (m)");

    for(String s:artists)
    {
        if(s.indexOf("(b)")!=-1) bnum++;
        if(s.indexOf("(m)")!=-1) mnum++;
        if(s.indexOf("(f)")!=-1) fnum++;
    }

    System.out.println("The number of male artists is: " + mnum);
    System.out.println("The number of female artists is: " + fnum);
    System.out.println("The number of bands is: " + bnum);
}