Error when trying to use conditional structure equality in java

Question

The code below is giving error in line if (sexo = 1){, can anyone explain to me why?

int sexo = 0, sexoF = 0, sexoM = 0, bom = 0, ruim = 0;

while (sexo != -1){

    System.out.println("Digite o sexo: ");

    System.out.println("[1] Homem");

    System.out.println("[2] Mulher");

    System.out.println("Digite -1 para sair")

    if (sexo = 1){ 
        ++sexoM;
    } else {
        ++sexoF;