java 笔试 面试 试题 计算机.docx

试题1已知变量a和obj的定义如下：Object a1 = “a”, “b”, “c” ;Object obj = a1;则下面语句运行时会抛出异常的是( )。A. Object a2 = (Object)obj;B. String str1 = (String)(Object)obj)1C. String a3 = (String)objD. String str2 = (String)a12 试题2已知类Foo的定义如下：public class Foo int value;Foo(int value) this.value = value;运行下面程序段：Foo a1 = new Foo(1), new Foo(2), new Foo(3) ;Foo a2 = new Fooa1.length;System.arraycopy(a1, 0, a2, 0, a1.length);System.out.println(a1 = a2) + “,” + (a11 = a21);控制台输出的结果是( )。A. false,trueB. false,falseC. true,trueD. true,false 试题3已知类Foo的定义如下：public class Foo int value;Foo(int value) this.value = value;public boolean equals(Object obj) if (obj instanceof Foo) Foo foo = (Foo) obj;return value = foo.value; else return false;运行下面程序段：ArrayList list = new ArrayList();HashSet set = new HashSet();list.add(new Foo(1);set.add(new Foo(1);System.out.println(list.contains(new Foo(1) + “,”+ set.contains(new Foo(1);控制台输出的结果是( )。A.true,falseB. true,trueC. false,falseD. false,true 试题4已知类A、B、C和接口D的定义如下：public class Apublic class B extends A implements D public class C extends A public interface D 变量a、b、c、d的定义如下：A a = new A(); B b = new B();C c = new C(); D d = null;则下列语句会有编译错误的是( )。A. a = b;B. d = b;C. d = (D)a;D. c = (C)b; 试题5运行如下代码：class COne public void f() System.out.println(“COne.f”);class CTwo extends COnepublic void f() System.out.println(“CTwo.f”);class CThree public void g(COne one) System.out.println(“g(Cone)”);one.f();public void g(CTwo two) System.out.println(“g(Ctwo)”);two.f();public class Main public static void main(String args) COne one = new CTwo();CThree three = new CThree();three.g(one);控制台输出的结果是( )。 A. g(Cone)CTwo.fB. g(Cone)COne.fC. g(Ctwo)CTwo.fD. g(Ctwo)COne.f 试题6运行如下代码class Foo private int value = 5;public Foo() System.out.println(“Foo()”);System.out.println(value);class Bar extends Fooprivate int value = 10;public Bar() System.out.println(“Bar()”);System.out.println(value);public class Main public static void main(String args) Bar bar = new Bar();控制台输出的结果是( )。A.Bar()10Foo()5B. Foo()5Bar()10C. Bar()5Foo()10D. Foo()10Bar()5 试题7实现Point类的equals方法，具体逻辑为：“成员变量x和y分别相等的Point对象被视为相等”。public class Point private int x;private int y;public boolean equals(Object obj) 以下代码正确的是( )。A.if(obj.x = this.x | obj.y = this.y)return true;return false;B.if(obj.x = this.x & obj.y = this.y)return true;return false;C.if(!(obj instanceof Point) return false;if(Point)obj).x = (Point)obj).y & this.x = this.y)return true;return false;D.if(!(obj instanceof Point) return false;if(Point)obj).x = this.x & (Point)obj).y = this.y)return true;return false; 试题8运行如下代码：List list = new ArrayList();/向list中插入内容1,2,3,4,5,6list.set(2, list.set(5,list.get(2)System.out.println(list);控制台的输出结果是( )。A. 1, 2, 5, 4, 5, 2B. 1, 5, 3, 4, 2, 6C. 1, 2, 6, 4, 5, 3D. 1, 2, 3, 4, 5, 3 试题9运行如下代码：List list = new ArrayList();/向list中插入内容1,2,3,4,5,6 list.subList(2, 5).clear();System.out.println(list);控制台的输出结果是( )。A. 1, 2, 3, 6B. 1, 2C. 1, 2, 3D. 1, 2, 6 试题10题示代码的功能为：将两个有序的ArrayList合并为一个有序的ArrayList。对于两个存放Integer对象的ArrayList，内容分别为：list1：1,3,4,6,8 和 list2：2,5,9合并后的list3: 1,2,3,4,5,6,8,9List list3 = new ArrayList();int size = list1.size() + list2.size();for (int i = 0, j = 0, k = 0; k size; k+) System.out.println(list3);完成该功能应该填入的代码是( )。A.if (j = list2.size() | i list1.size()& list1.get(i) = list2.size() | i list1.size()& list1.get(i) = list2.size() | i list2.get(j) list3.add(list1.get(i+); else list3.add(list2.get(j+);D.if (j = list2.size() | i list1.size()| list1.get(i) list2.get(j) list3.add(list1.get(i+); else list3.add(list2.get(j+); 试题11运行如下代码：String ss = abcdefcde;int i = ss.indexOf(cde, 3);System.out.println(i);控制台输出的结果是( )。A. 6B. 3C. 2D. 7 试题12运行如下代码：String ss = abcdefcde;char cc = ss.charAt(3);System.out.println(cc);控制台输出的结果是( )。A. bB. eC. cD. d 试题13运行如下代码：String ss = abcdefcde;String s = ss.substring(2, 4);System.out.println(s);控制台输出的结果是( )。A. cdefB. cdC. cdeD. bcde 试题14下面说法正确的是A. 一个接口可以继承另外一个接口B. 一个类只能实现一个接口C. Java语言支持多继承D. 抽象类中的非抽象方法不可以调用其抽象方法 试题15下面的代码用于输出字符数组ch中字符出现的种类和个数，应该填入的代码是（）。public static void main(String args) char ch = a, c, a, b, c, b ;HashMap map = new HashMap();for (int i = 0; i ch.length; i+) System.out.println(map);A.if (map.contains(chi) map.put(chi, map.get(chi) + 1); else map.put(chi, 1);B.if (map.contains(chi) map.put(chi, (Integer) map.get(chi) + 1); else map.put(chi, 1);C.if (map.containsKey(chi) map.put(chi, (int) map.get(chi) + 1); else map.put(chi, 1);D.if (map.containsKey(chi) map.put(chi, (Integer) map.get(chi) + 1); else map.put(chi, 1); 试题16关于String和StringBuffer对象描述，错误的是A. StringBuffer是可变对象，而String是不可变对象B. 对字符串进行删除、插入等可变操作时一般使用StringBufferC. String对象池的作用在于提升效率D. StringBuffer的append方法将返回一个全新的StringBuffer对象 试题17已知静态方法random(int n)用于返回大于等于0且小于n的随机整数。利用此函数实现对ArrayList的“洗牌”操作。所谓“洗牌”操作，即将ArrayList元素的位置随机打乱，使得ArrayList的每个元素的位置在除原位置外的其他随机位置上。应该填入的代码是public class shuffleUtils public static void shuffle(ArrayList list) public static int random (int n) A.for (int i = list.size(); i 1; i) int j = random(i);list.set(j,list.get(i-1);B.for (int i = list.size(); i 1; i) int j = random(i);list.set(i-1, list.set(j,list.get(i-1);C.for (int i = list.size(); i 1; i) int j = random(i);list.set(i-1,list.get(j);D.for (int i = list.size(); i 1; i) int j = random(i);list.set(i, list.set(j,list.get(i); 试题18ArrayList的初始化内容如下：ArrayList list = new ArrayList();list.add(“java”);list.add(“aaa”);list.add(“java”);list.add(“java”);list.add(“bbb”);下面可以删除list中所有的“java”的代码是：A.for (int i = list.size() 1; i = 0; i) if (“java”.equals(list.get(i) list.remove(i);B.for (int i = 0; i list.size() 1; i+) if (“java”.equals(list.get(i) list.remove(i);C.list.remove(“java”);D.list.removeAll(“java”); 试题19下面字符串和正则表达式 JQK2a-z0-9