Java字符串比较方法equals的空指针异常的解决

public class StringEqual {

 public static void equal1(String i, String j) {
 try {
  if(i.equals(j)) {
  System.out.println("equal1相等");
  }
 } catch (Exception ex) {
  System.out.println("equal1 异常：");
  ex.printStackTrace();
 } finally {
  System.out.println("equal1结束");
 }
 }

 public static void equal2(String i, String j) {
 try {
  if(j.equals(i)) {
  System.out.println("equal2相等");
  }
 } catch (Exception ex) {
  System.out.println("equal2异常：");
  ex.printStackTrace();
 } finally {
  System.out.println("equal2结束");
 }
 }
 
 public static void main(String[] args) {
 equal1(null,"abc");
 equal2(null,"abc");
  }
}

public boolean equals(Object anObject) {
  if (this == anObject) {
    return true;
  }
  if (anObject instanceof String) {
    String anotherString = (String)anObject;
    int n = value.length;
    if (n == anotherString.value.length) {
      char v1[] = value;
      char v2[] = anotherString.value;
      int i = 0;
      while (n-- != 0) {
        if (v1[i] != v2[i])
          return false;
        i++;
      }
      return true;
    }
  }
  return false;
}