JAVA复习题201001答案

题目以下代码:1. public class TestString1{2. public static void main(String[] args){3. String str = "420";4. str += 42;5. System.out.print(str);6. }7. }输出什么?以下代码:1. public class Test{2. public static void main(String[] args){3. int x = 5;4. boolean b1 = true;5. boolean b2 = false;6.7. if((x==4) && !b2)8. System.out.print("1 ");9. System.out.print("2 ");10. if((b2=true) && b1)11. System.out.print("3 ");12. }13. }运行结果是什么?以下代码:22. public void go(){23. String o = "";24. z:25. for(int x=0; x<3; x++){26. for(int y=0; y<2; y++){27. if(x == 1) break;28. if(x==2 && y==1) break z;29. o = o + x + y;30. }31. }32. System.out.println(o);33. }go()方法被调用后，产生什么结果？以下代码:10. int x = 0;11. int y = 10;12. do{13. y--;14. ++x;15. }while(x < 5);16. System.out.print(x + "," + y);运行结果是?以下代码:1. public class Breaker{2. static String o = "";3. public static void main(String[] args){4. z:5. o = o + 2;6. for(int x=3; x<8; x++){7. if(x == 4) break;8. if(x == 6) break z;9. o = o + x;10. }11. System.out.println(o);12. }13. }运行结果是?以下代码:1. public class Spock{2. public static void main(String[] args){3. Long tail = 2000L;4. Long distance = 1999L;5. Long story = 1000L;6. if((tail>distance) ^ ((story*2)==tail))7. System.out.print("1");8. if((distance+1 != tail) ^ ((story*2)==distance))9. System.out.print("2");10. }11. }运行结果是?以下代码:1. import java.util.*;2. public class Quest{3. public static void main(String[] args){4. String[] colors =5. {"blue","red","green","yellow","orange"};6. Arrays.sort(colors);7. int s2 = Arrays.binarySearch(colors, "orange");8. int s3 = Arrays.binarySearch(colors, "violet");9. System.out.print(s2 + "" + s3);10. }11. }运行结果是?以下代码:1. class Alligator{2. public static void main(String[] args){3. int[]x[] = {{1,2},{3,4,5},{6,7,8,9}};4. int[][]y = x;5. System.out.print(y[2][1]);6. }7. }运行结果是?以下代码:1. public class Barn{2. public static void main(String[] args){3. new Barn.go("hi", 1);4. new Barn.go("hi", "world", 2);5. }6. public void go(String... y, int x){7. System.out.print(y[y.length-1] + " ");8. }9. }运行结果是?以下代码:5. class Atom{6. Atom(){System.out.print("atom ");}7. }8. class Rock extends Atom{9. Rock(String type){System.out.print(type);}10. }11. public class Mountain extends Rock{12. Mountain(){13. super("granite ");14. new Rock("granite ");15. }16. public static void main(String[] a){new Mountain();}17. }运行结果是?以下代码:1. class X{2. X(){System.out.print(1);}3. X(int x){4. this();5. System.out.print(2);6. }7. }8. public class Y extends X{9. Y(){10. super(6);11. System.out.print(3);12. }13. Y(int y){14. this();15. System.out.println(4);16. }17. public static void main(String[] a){new Y(5);}18. }运行结果是?以下代码:1. public class A{2. public void doit(){3. }4. public String doit(){5. return "a";6. }7. public double doit(int x){8. return 1.0;9. }10. }运行结果是?以下代码:1. public class Base{2. public static final String FOO = "foo";3. public static void main(String[] args){4. Base b = new Base();5. Sub s = new Sub();6. System.out.print(Base.FOO);7. System.out.print(Sub.FOO);8. System.out.print(b.FOO);9. System.out.print(s.FOO);10. System.out.print(((Base)s).FOO);11. }12. }13. class Sub extends Base{public static final String FOO = "bar";}运行结果是?以下代码:21. abstract class C1{22. public C1(){System.out.print(1);}23. }24. class C2 extends C1{25. public C2(){System.out.print(2);}26. }27. class C3 extends C2{28. public C3(){System.out.print(3);}29. }30. public class Ctest{31. public static void main(String[] a){new C3();}32. }运行结果是?以下代码:1. public class KungFu{2. public static void main(String[] args){3. Integer x = 400;4. Integer y = x;5. x++;6. StringBuilder sb1 = new StringBuilder("123");7. StringBuilder sb2 = sb1;8. sb1.append("5");9. System.out.println((x == y) + " " + (sb1 == sb2));10. }11. }运行结果是?1. class A{2. public String doit(int x, int y){3. return "a";4. }5.6. public String doit(int... vals){7. return "b";8. }9. }给出以下代码，运行产生什么结果？:25. A a = new A();26. System.out.println(a.doit(4, 5));以下代码:1. package test;2.3. class Target{4. public String name = "hello";5. }可以直接访问和修改name变量值的是?以下代码:11. abstract class Vehicle{public int speed(){return 0;}}12. class Car extends Vehicle{public int speed(){return 60;}}13. class RaceCar extends Car{public int speed(){return 150;}} ...21. RaceCar racer = new RaceCar();22. Car car = new RaceCar();23. Vehicle vehicle = new RaceCar();24. System.out.println(racer.speed() + ", " + car.speed()25. + ", " + vehicle.speed());运行的结果是?关于以下代码:5. class Building{}6. public class Barn extends Building{7. public static void main(String[] args){8. Building build1 = new Building();9. Barn barn1 = new Barn();10. Barn barn2 = (Barn)build1;11. Object obj1 = (Object)build1;12. String str1 = (String)build1;13. Building build2 = (Building)barn1;14. }15. }哪一个是正确的?以下代码:21. class Money{22. private String country = "Canada";23. public String getC(){return country;}24. }25. class Yen extends Money{26. public String getC(){return super.country;}27. }28. public class Euro extends Money{29. public String getC(){return super.getC();}30. public static void main(String[] args){31. System.out.print(new Yen().getC() + " " + new Euro().getC());32. }33. }运行结果是?以下代码:10. interface Foo{}11. class Alpha implements Foo{}12. class Beta extends Alpha{}13. public class Delta extends Beta{14. public static void main(String[] args){15. Beta x = new Beta();16. //insert code here17. }18. }以下哪个代码插入第16行会抛出ng.ClassCastException异常?以下代码:31. class Foo{32. public int a = 3;33. public void addFive(){ a += 5; System.out.print("f "); }34. }35. class Bar extends Foo{36. public int a = 8;37. public void addFive(){this.a += 5; System.out.print("b ");}38. }通过以下调用:Foo f = new Bar();f.addFive();System.out.println(f. a);运行的结果是?Given:1. class TestA{2. public void start(){System.out.println("TestA");}3. }4. public class TestB extends TestA{5. public void start(){System.out.println("TestB");}6. public static void main(String[] args){7. ((TestA)new TestB()).start();8. }9. }What is the result?10. class Nav{11. public enum Direction { NORTH, SOUTH, EAST, WEST }12. }13. public class Sprite{14. //insert code here15. }以下哪个代码插入在14行，可以让Sprite class编译通过?以下代码:5. class Payload{6. private int weight;7. public Payload (int w){weight = w;}8. public void setWeight(int w){weight = w;}9. public String toString(){return Integer.toString(weight);}10. }11. public class TestPayload{12. static void changePayload(Payload p){/* insert code */}13. public static void main(String[] args){14. Payload p = new Payload(200);15. p.setWeight(1024);16. changePayload(p);17. System.out.println("p is " + p);18. }}哪个代码片段插入12行,使程序实行结果为420?以下代码:11. public static void test(Sting str){12. int check = 4;13. if(check = str.length()){14. System.out.print(str.charAt(check -= 1) + ", ");15. }else{16. System.out.print(str.charAt(O) + ", ");17. }18. }通过下列调用，执行结果是什么？21. test("four");22. test("tee");23. test("to");15. public class Pass2{16. public static void main(String[] args){17. int x = 6;18. Pass2 p = new Pass2();19. p.doStuff(x);20. System.out.print(" main x = " + x);21. }22.23. void doStuff(int x){24. System.out.print(" doStuff x = " + x++);25. }26. }在命令行输入以下指令，产生什么结果？javac Pass2.javajava Pass2 5String s=new String("1");String t=new String("1");则执行语句System.out.println(s==t);的输出结果为如果A类继承B类则下列哪个说法最可能是正确的?执行下列代码后变量a的值为:boolean a=false;boolean b=false&&(a=(5>3));下列java程序设计中编译错误的是:在类中入口方法main的写法正确的为下列关于double,long,float类型可表示的数值范围的大小顺序正确的是执行下列语句后输出的结果为:int a=0;while(a<10){a++;}System.out.println(a);执行下列语句输出的结果为：int a=6;if(a<=5)if(a<5) System.out.println("a<5");else System.out.println("a>5");下列哪个选项是java语言所不具备的以下哪个是Runnable接口中定义的方法？抽象方法定义和常量值的集合是下列不属于条件控制语句的是下列说法正确的是对象中必有属性和方法选项4242046242042D 231 22 3D 00001000120C 00012021编译错误5，65，5B 6，56，6232342352345235723457编译错误1212编译错误没有输出E2-12-42-5C 3-13-43-5编译错误运行时发生异常23467E 编译错误hi hihi worldworld world编译错误D编译错误atom granitegrantie graniteatom granite granite运行时发生异常atom granite atom granite F 131341234C 213421434321运行时发生异常第七行错误第四行错误C 编译正确、运行正常foofoofoofoofoofoobarfoobarbarfoobarfoofoofoofoobarfoobarfoo D barbarbarbarbarfoofoofoobarbarfoofoofoobarfoo32332123D 321true truefalse true B true falsefalse false编译错误运行时发生异常A. Line 26 prints "a" to System.out.AB. Line 26 prints "b" to System.out.运行时发生异常第6行编译错误any classonly the Target classany class in the test package C any class that extends Target0, 0, 0150, 60, 0编译错误150, 150, 150D 运行时发生异常如果删除第十行，编译可以通过。