Extract substring from a string

问题:

what is the best way to extract a substring from a string in android?

回答1:

If you know the Start and End index, you can use

String substr=mysourcestring.substring(startIndex,endIndex);

If you want to get substring from specific index till end you can use :

String substr=mysourcestring.substring(startIndex);

If you want to get substring from specific character till end you can use :

String substr=mysourcestring.substring(mysourcestring.indexOf("characterValue"));

If you want to get substring from after a specific character, add that number to .indexOf(char):

String substr=mysourcestring.substring(mysourcestring.indexOf("characterValue") + 1);

回答2:

substring():

str.substring(startIndex, endIndex); 

回答3:

Here is a real world example:

String hallostring = "hallo";
String asubstring = hallostring.substring(0, 1); 

In the example asubstring would return: h

回答4:

There is another way , if you want to get sub string before and after a character

String s ="123dance456";
String[] split = s.split("dance");
String firstSubString = split[0];
String secondSubString = split[1];

check this post- how to find before and after sub-string in a string

回答5:

use text untold class from android:
TextUtils.substring (charsequence source, int start, int end)

回答6:

You can use subSequence , it's same as substr in C

 Str.subSequence(int Start , int End)

回答7:

you can use this code

    public static String getSubString(String mainString, String lastString, String startString) {
    String endString = "";
    int endIndex = mainString.indexOf(lastString);
    int startIndex = mainString.indexOf(startString);
    Log.d("message", "" + mainString.substring(startIndex, endIndex));
    endString = mainString.substring(startIndex, endIndex);
    return endString;
}

in this mainString is a Super string.like "I_AmANDROID.Devloper" and lastString is a string like"." and startString is like"_". so this function returns "AmANDROID". enjoy your code time.:)

回答8:

substring(int startIndex, int endIndex)

If you don't specify endIndex, the method will return all the characters from startIndex.

startIndex : starting index is inclusive

endIndex : ending index is exclusive

Example:

String str = "abcdefgh"

str.substring(0, 4) => abcd

str.substring(4, 6) => ef

str.substring(6) => gh

回答9:

The best way to get substring in Android is using (as @user2503849 said) TextUtlis.substring(CharSequence, int, int) method. I can explain why. If you will take a look at the String.substring(int, int) method from android.jar (newest API 22), you will see:

public String substring(int start) {
    if (start == 0) {
        return this;
    }
    if (start >= 0 && start <= count) {
        return new String(offset + start, count - start, value);
    }
    throw indexAndLength(start);
}

Ok, than... How do you think the private constructor String(int, int, char[]) looks like?

String(int offset, int charCount, char[] chars) {
    this.value = chars;
    this.offset = offset;
    this.count = charCount;
}

As we can see it keeps reference to the "old" value char[] array. So, the GC can not free it.

In the newest Java it was fixed:

String(int offset, int charCount, char[] chars) {
    this.value = Arrays.copyOfRange(chars, offset, offset + charCount);
    this.offset = offset;
    this.count = charCount;
}

Arrays.copyOfRange(...) uses native array copying inside.

That's it :)

Best regards!