一份Java基础知识笔试题附答案

 1/**
 2如果运行JavaDemo,什么样的信息会打印出来?
 3*/
 4public class Demo {
 5  public static void main(String[] args) {
 6    Integer intObj = Integer.valueOf(args[args.length -1]);
 7    int i = intObj.intValue();
 8    if (args.length > 1){
 9      System.out.println(i);
10    }
11    if (args.length > 0){
12      System.out.println(i-1);
13    }else {
14      System.out.println(i-2);
15    }
16  }
17}

 1/**
 2运行以下代码会输出什么信息?
 3*/
 4 static class Test{
 5    static int i ;
 6    public static void main(String[] args) {
 7      while (i < 0){
 8        i--;
 9      }
10      System.out.println(i);
11    }
12  }
13}

 1/**
 2运行以下代码会输出什么信息
 3*/
 4  static class Test2{
 5    public static void main(String[] args) {
 6      int i = 0;
 7      boolean t = true;
 8      boolean f = false,b;
 9      b = (t || ((i++) == 0));
10      b = (f || ((i += 2) > 0 ));
11      System.out.println("i = " + i);
12    }
13  }
14}

 1/**
 2以下代码会输出什么信息?
 3*/
 4  static class Test3{
 5    public static void main(String[] args) {
 6      int i,j,k,l = 0;
 7      k = l++;
 8      j = ++k;
 9      i = j++;
10      System.out.println("i = " + i);
11    }
12  }

 1/**
 2阅读以下代码片段,选择正确的答案
 3*/
 4  static class Test4{
 5    public static void main(String[] args) {
 6      Integer num1 = 10;
 7      Integer num2 = Integer.valueOf(10);
 8      Integer num3 = new Integer(10);
 9      if (num1 == num2){
10        System.out.println("Equal");
11      }else {
12        System.out.println("Not Equal");
13      }
14      if (num1 == num3){
15        System.out.println("Equal");
16      }else {
17        System.out.println("Not Equal");
18      }
19    }
20  }

 1/**
 2下面代码执行后,变量nunber的值是多少?
 3*/
 4  static class  Test5 {
 5    public static void main(String[] args) {
 6      int number = 0;
 7      int number2 = 12;
 8      while (number < number2) {
 9        number = number +1;
10      }
11      System.out.println("number = " + number);
12    }
13  }
14}

 1/**
 2那两个语句是等效的?
 3*/
 4  static  class Test6{
 5    public static void main(String[] args) {
 6      System.out.println(16*4);
 7      System.out.println(16 >> 2);
 8      System.out.println(16/2^2);
 9      System.out.println(16>>>2);
10    }
11  }
12}

 1/**
 2以下代码的输出结果是?
 3*/
 4  static class Test7{
 5    public static void main(String[] args) {
 6      String a = "newspaper";
 7      a = a.substring(5,7);
 8      char b = a.charAt(1);
 9      a = a + b;
10      System.out.println("a = " + a);
11    }
12  }

 1 static class X{
 2    public static void main(String[] args) {
 3      X x = new X();
 4      X x2 = mi(x);
 5      X x4 = new X();
 6      doComplexStuff();
 7    }
 8    private static void doComplexStuff() {
 9
10    }
11    private static X mi(X mx) {
12      mx= new X();
13      return mx;
14    }
15  }
16}

1static class Test8{
2  public static void main(String[] args) {
3    Dog[][] theDogs = new Dog[3][];
4    System.out.println(theDogs[2][0].toString());
5  }
6}

1float f1 = -343;
2float f2 = 3.14;
3float f3 = 0*12345;
4float f4 = 42e7;
5float f5 = 2001.0D;
6float f6 = 2.18F;

 1static  class Test10{
 2  public static void main(String[] args) {
 3    int i = 1,j = 10;
 4    do {
 5      if (i > j){
 6        break;
 7      }
 8      j--;
 9    }while (++i < 5 );
10    System.out.println("i = " + i + "and j = " + j);
11  }
12}

 1static  class Test11{
 2  public static void main(String[] args) {
 3    int x = 0;
 4    int y = 0;
 5    for (int i = 0; i < 5; i++) {
 6      if ((++x > 2) || (++y >2)){
 7        x++;
 8      }
 9    }
10    System.out.println(x + "" + y);
11  }
12}

 1public class Demo4 extends Thread{
 2  final StringBuffer sb1 = new StringBuffer();
 3  final StringBuffer sb2 = new StringBuffer();
 4
 5  public static void main(String[] args) {
 6    final Demo4 h = new Demo4();
 7    new Thread(){
 8      @Override
 9      public void run() {
10        synchronized (this){
11          h.sb1.append("A");
12          h.sb2.append("B");
13          System.out.println(h.sb1);
14          System.out.println(h.sb2);
15        }
16      }
17    }.start();
18    new Thread(){
19      @Override
20      public void run() {
21        synchronized (this){
22          h.sb1.append("D");
23          h.sb2.append("C");
24          System.out.println(h.sb2);
25          System.out.println(h.sb1);
26        }
27      }
28    }.start();
29  }
30}