如何在java中定义一个字符串数组并在switch case中使用它

Question

Hi dear friends, I want to define a String array in java and use every cells of that array in switch-case in java to count every string elements.for example can you you help me to fix it thanks.

int i=20;
String [] str =new String[i];
string[0]="This";
string[1]="is";
string[2]="a";
string[3]="Test";
string[4]="This";
string[5]="This";
string[6]="a";
string[7]="a";
string[8]="a";
string[20]="Test";
switch(i)
{
case(0):this++
break;
case(1):is++
break;
case(2):a++
break;
case(3):test++
break;
}

Answer 1

While i don't really understand what you are trying to do, here are my two cents. You are probably getting an ArrayIndexOutOfBoundsException . This is because when you create an array of size 20 , it can hold exactly 20 items. From range 0 to 19 . So trying to do string[20]="Test"; will give an error because it's out of bounds.

Answer 2

Trying to enumerate all the different possible strings in the array is generally a bad idea and not the correct way to write your program. Sure your example works, but what would happen if your set of possible strings was not just {'this', 'is', 'a', 'test'}, but instead had say 10000 elements? What if you didn't know exactly what String elements were in the array? As a previous user mentioned, you want to use a HashMap<String, Integer> .

String[] arr = yourStringArray; //wherever your Strings are coming from
Map<String, Integer> strCounts = new HashMap<String, Integer>; //this stores the strings you find
for (int i = 0; i < arr.length; i++) {
    String str = arr[i];
    if (strCounts.containsKey(str)) {
        strCounts.get(str) += 1; //if you've already seen the String before, increment count
    } else {
        strCounts.put(str, 1); //otherwise, add the String to the HashMap, along with a count (1)
    }
}

Answer 3

I would do it this way:

int count;
String currentWord;
Map<String, Integer> wordMap = new HashMap<>();
StringTokenizer tokenizer = new StringTokenizer(mySentence);
while(tokenizer.hasNext()){
count = null;
currentWord = tokenizer.nextToken();
count = wordMap.get(currentWord);
if(count == null) wordMap.put(currentWord, 1);
else wordMap.put(currentWord, ++count);
}