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private static void generarbanca() {

    int valorcartabanca;

    do {

        int valorcartabancamin = 1;// from one to 11

        valorcartabanca = valorcartabancamin + (byte) (Math.random() * 10);

    }while (valorcartabanca<15);

}

valorcartamin is the minimun number that I want to generate for the crupier, so the problem is that program get in a infite loop.
I want it to generate number until 15 point score is reached and count the number needed till 15 and so on.

1 + (Math.random() * 10) will always be less than 15. Did you want to write

valorcartabanca += valorcartabancamin + (byte) (Math.random() * 10);

Note the += instead of a simple =.

You need to extract the initialization of valorcartabancamin from the loop, and in addition you need to keep the current value of valorcartabanca, so use the += operator:

 private static void generarbanca() {

    int valorcartabancamin = 1;// desde uno hasta 11

    int valorcartabanca = 0;

    do {

        valorcartabanca += valorcartabancamin + (byte) (Math.random() * 10);

    } while (valorcartabanca<15);

}

you are not accumulating valorcartablanca.
try

int valorcartabanca = 1;

do {    

    valorcartabanca = valorcartabancamin + (byte) (Math.random() * 10);

}while (valorcartabanca<15);