九十九八桥本子:谁能找出这个Java程序的4个错误啊?

public class DNASequence {

private String sequence;

private int numberOfA;

private int numberOfT;

private int numberOfC;

private int numberOfG;

public static void main(String[] args) {

String s = "ATTATCGGGGTAA";
DNASequence dnaSequence = new DNASequence(s);

if ((dnaSequence.getNumberOfA() == 4)
&& (dnaSequence.getNumberOfT() == 4)
&& (dnaSequence.getNumberOfC() == 1)
&& (dnaSequence.getNumberOfG() == 4)) {
System.out.println("Test case 1: get methods passed\n");
} else {
System.out.println("Test case 1: get methods failed !!!\n");
}

if (dnaSequence.twoConsecutive('T')) {
System.out.println("Test case 2: method twoConsecutive passed\n");
} else {
System.out.println(
"Test case 2: method twoConsecutive failed !!!\n");
}

if (dnaSequence.twoConsecutive('A')) {
System.out.println("Test case 3: method twoConsecutive passed\n");
} else {
System.out.println(
"Test case 3: method twoConsecutive failed !!!\n");
}

if (!dnaSequence.twoConsecutive('C')) {
System.out.println("Test case 4: method twoConsecutive passed\n");
} else {
System.out.println(
"Test case 4: method twoConsecutive failed !!!\n");
}
}

public DNASequence(String initialSequence) {

sequence = initialSequence;
countNucleotides();
}

private void countNucleotides() {

int numberOfA = 0;
int numberOfT = 0;
int numberOfC = 0;
int numberOfG = 0;

int index = 0;

while (index < sequence.length()) {

char nucleotide = sequence.charAt(index);

if (nucleotide == 'A') {
numberOfA++;
} else if (nucleotide == 'T') {
numberOfT++;
} else if (nucleotide == 'C') {
numberOfC++;
} else if (nucleotide == 'G') {
numberOfC++;
}
index++;
}

return;
}

public int getNumberOfA( ) {

return numberOfA;
}

public int getNumberOfT( ) {

return numberOfT;
}

public int getNumberOfC( ) {

return numberOfC;
}

public int getNumberOfG( ) {

return numberOfG;
}

public boolean twoConsecutive(char input) {

int index = 1;

while (index < sequence.length() - 1) {

int indexOfFirstNucleotide = index - 1;

char firstNucleotide = sequence.charAt(indexOfFirstNucleotide);
char secondNucleotide = sequence.charAt(index);

if ((firstNucleotide == input) || (secondNucleotide == input)) {

return true;

}
index++;
}

return false;
}
}