Overriding methods for a custom filter input stream in java

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I have stumbled upon this problem:

So I have created a class for a custom filtered input stream and overridden the read() method. I also need to override the read(byte[] b) method in a way that it uses the criteria that I had defined for the read() method but it does not do. I have tried many ways.

Java

public class CustomInput extends FilterInputStream{

    protected CustomInput(InputStream in) {
        super(in);
    }
    
    @Override
    public int read() throws IOException {
        int y=super.read();
        if(y==65) {
            return 194;
        } else {
            return y;
        }
    }

    @Override
    public int read(byte[] b) throws IOException{
    }
}

I do not know how to make each byte that the method reads whether it is a 65 and return a 194, and if it is not a 65 return whatever it reads just like I have defined in the read() method.

What I have tried:

I have tried calling the read() method for each byte but I can not get it working.

I made it work using a while loop but I really want to have a separate custom method for the read(byte[] b) method.

Posted 3-Nov-21 13:09pm

Eric1899599

Updated 4-Nov-21 2:21am

Richard Deeming

v2

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Richard MacCutchan 4-Nov-21 5:18am

Don't use numbers to represent character values. Use the proper characters, e.g. 'A' and 'Â', so people can understand what the code is supposed to be doing.

Also, you have not explained what the actual problem is.

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Richard MacCutchan · Accepted Answer · 2021-11-04T02:21:00

Solution 1

You cannot use your read method as it gets its input from super.read. So you need to do the same for an array:

Java

public int read(byte[] b) throws IOException{
    super.read(b);
    for (int i = 0; i < b.length; ++i){
        if (b[i] = 'A'){
            b[i] = 'Â';
        }
    }
}

Posted 4-Nov-21 2:21am

Richard MacCutchan

Comments

Eric1899599 4-Nov-21 18:09pm

Thank you very much.
I have changed it a little and it worked like this.

I was just wondering why does it still work if it says "return 0".
It does not work if I do not put a return statement obviously.

@Override
public int read(byte[] b) throws IOException{
super.read(b);
for (int i = 0; i < b.length; i++){
if (b[i] ==65){
b[i] = (byte) 194;
} if(b[i]==101) {
b[i]=(byte) 233;
}
}
return 0;
}

Richard MacCutchan 5-Nov-21 4:04am

Why are you still using decimal numbers instead of characters in your code?

The reason it will not work if you do not have return 0 at the end is because the method's declaration states that it returns an integer. So maybe you should check the documentation to see what actual value it is supposed to return.

Eric1899599 6-Nov-21 9:56am

Thank you very much for your response, could you please tell me why I should use characters instead of decimal numbers?

Richard MacCutchan 6-Nov-21 10:12am

Because it is a) common sense to use the correct variable type, and b) it makes your code easier to understand. How many people looking at that would know that 194 represents the character 'Â'?

Eric1899599 6-Nov-21 11:06am

Got that, thank you.