範例

public class ClassA {
public List methodA (boolean isTrue) {

ArrayList al = new ArrayList();
if (isTrue){
//...
return al;
}
return null;
}

}
解決方案
傳回空的 ArrayList,而不是空值

public class ClassA {
public List methodA (boolean isTrue) {

ArrayList al = new ArrayList();
if (isTrue){
//...
return al;
}
return new ArrayList(0);
}

}