多项选择题
单项选择题
public class Test { private static int[] x; public static void main(String[] args) { System.out.println(x[0]); } } What is the result?()
public class Person { private String name, comment; private int age; public Person(String n, int a, String c) { name = n; age = a; comment = c; } public boolean equals(Object o) { if(! (o instanceof Person)) return false; Person p = (Person)o; return age == p.age && name.equals(p.name); } } What is the appropriate definition of the hashCode method in class Person?()
interface Animal { void soundOff(); } class Elephant implements Animal { public void soundOff() { System.out.println(“Trumpet”); } } class Lion implements Animal { public void soundOff() { System.out.println(“Roar”); } } class Alpha1 { static Animal get( String choice ) { if ( choice.equalsIgnoreCase( “meat eater” )) { return new Lion(); } else { return new Elephant(); } } } Which compiles?()
20. public float getSalary(Employee e) { 21. assert validEmployee(e); 22. float sal = lookupSalary(e); 23. assert (sal>0); 24. return sal; 25. } 26. private int getAge(Employee e) { 27. assert validEmployee(e); 28. int age = lookupAge(e); 29. assert (age>0); 30. return age; 31. } Which line is a violation of appropriate use of the assertion mechanism?()
switch (i) { default: System.out.printIn(“Hello”); } What is the acceptable type for the variable i?()
Float pi = new Float(3.14f); if(pi>3) { System.out.print(”pi is bigger than 3. “); } else { System.out.print(”pi is not bigger than 3. “); } finally { System.out.println(”Have a nice day.”); } What is the result?()
25.intx=12; 26. while (x < 10) { 27. x--; 28. } 29. System.out.print(x); What is the result?()
14. DateFormat df; 15. Date date = new Date(); 16. //insert code here 17. String s = df.format( date); Which two,inserted independently at line 16, allow the code to compile?()
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