How to generate multiple nested repeat structures with methods

Question

need to generate several nested structures (26) wanted to know how to do this with methods pro code not get too big an example of the structure I need with 4 nested:

public static void main(String[] args) {
    String[] vet={"1","2","3","4"};
    for(int i=0;i<4;i++)
        for(int j=0;j<4;j++) if(i!=j)
            for(int k=0;k<4;k++) if(j!=k && i!=k)
                for(int l=0;l<4;l++) if(k!=l && i!=l && j!=l)
                    System.out.println(vet[i]+vet[j]+vet[k]+vet[l]);

}