importjava.util.*;
classKeyMaster{
publicinti;
publicKeyMaster(inti){this.i=i;}
publicbooleanequals(Objecto){returni==((KeyMaster)o).i;}
publicinthashCode(){returni;}
}
publicclassMapIt{
publicstaticvoidmain(String[]args){
Setset=newHashSet();
KeyMasterk1=newKeyMaster(1);
KeyMasterk2=newKeyMaster(2);
set.add(k1);set.add(k1);
set.add(k2);set.add(k2);
System.out.print(set.size()+:”);
k2.i=1;
System.out.print(set.size()+:”);
set.remove(k1);
System.out.print(set.size()+:”);
set.remove(k2);
System.out.print(set.size());
}
}
Whatistheresult?()
第1题:
importjava.util.*;publicclassLetterASort{publicstaticvoidmain(String[]args){ArrayListstrings=newArrayList();strings.add(?aAaA”);strings.add(”AaA”);strings.add(?aAa”);strings.add(”AAaa”);Collections.sort(strings);for(Strings:strings){System.out.print(s+);}}}Whatistheresult?()
A.Compilationfails.
B.aAaAaAaAAaaAaA
C.AAaaAaAaAaaAaA
D.AaAAAaaaAaAaAa
E.aAaAaAaAaAAAaa
F.Anexceptionisthrownatruntime.
第2题:
在下列源代码文件Test.java中, ( )是正确的类定义。
A.public class test{
B.public class Test{ public int x=0;public int x=0; public test (intx) public Test (int x){ {this.x=x; this.x=x;} }} }
C.public class Test extends T1,T2{
D.protected class Test extends T2{ public int=0;public int x=0; public Test(int x){Public Test (int x){ this.x=x;this.x=x: }} }}
第3题:
7、以下程序的运行结果是()。 import java.util.*; public class Test{ public static void main(String[] args){ List<Integer> list= Arrays.asList(1,2,3,4); int sum=0; for(int s:list) sum+=s; System.out.println(sum); } }
A.1234
B.10
C.1,2,3,4
D.0
第4题:
importjava.util.*;publicclassPQ{publicstaticvoidmain(String[]args){PriorityQueuepq=newPriorityQueue();pq.add(”carrot”);pq.add(”apple”);pq.add(”banana”);System.out.println(pq.poll()+”:”+pq.peek());}}Whatistheresult?()
A.apple:apple
B.carrot:apple
C.apple:banana
D.banana:apple
E.carrot:carrot
F.carrot:banana
第5题:
8、下列程序执行的结果是___________。 import java.util.*; public class Example{ public static void main(String[] args){ String s="x,yy,123"; Scanner sc=new Scanner(s); while(sc.hasNext()){ System.out.print(sc.next()+" "); } } }
A.x yy
B.x,yy,123
C.x yy 123
D.x,yy