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详细介绍scjp考试指南包括基础语法和文件读取

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4.     }
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5.     public void itemStateChanged(ItemEvent ie) {
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6.       System.out.println("Item.");
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7.     }
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8.   }
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a. The code compiles without error.
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b. The code generates a compiler error at line 1.
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c. The code generates a compiler error at line 2.
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d. The code generates a compiler error at line 5.
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Q25
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A text field has a variable-width font. It is constructed by calling new TextField("iiiii"). What happens if you change the contents of the textfield to "wwwww"? (NOTE i is one of the narrowest characters, and w is one of the widest.)
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a. The text field becomes wider.
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b. The text field becomes narrower.
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c. The text field stays the same width; to see the entire contents you have to scroll using -> and <-.
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d. The text field stays the same width; to see you need to have a horizontal scroll bar.
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Q26
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Which statements about garbage collection are true? Select all valid answers
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a. You can directly free the memory allocated by an object.
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b. You can directly run the garbage collector whenever you want.
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c. The garbage collector informs your object when it is about to be garbage collected.
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d. The garbage collector runs in low-memory situations.
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Q27
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The setForeground() and setBackground() methods are defined in the following class
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a. Graphics
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b. Container
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c. Component
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d. Applet
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Q28
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What methods does JAVA define in the java.lang.Math class specifically for trigonometric calculations? Select all valid answers.
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a. cos()
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b. asin()
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c. arctan()
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d. sine()
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Q29
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Imagine that there are two exception classes called Exception1 and Exception2 that descend from the Exception class. Given these two class definitions,
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1.   class First {
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2.     void test() throws Exception1, Exception2 { . . . }
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3.   }
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4.   class Second extends First {
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5.     void test() { . . . }
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Create a class called Third that extends Second and defines a test() method. What exceptions can Third's test method throw? Select all valid answers.
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a. Exception1
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b. Exception2
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c. no checked exceptions
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d. any exceptions declared in the throws clause of the Third's test() method.
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Q30
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Given these code snippets,
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1.   Boolean b1 = new Boolean(true);
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2.   Boolean b2 = new Boolean(true);
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which expressions are legal JAVA expressions that return true? Select all valid answers.
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a. b1 == b2
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b. b1.equals(b2)
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c. b1 & b2
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d. b1 || b2
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Q31
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What will appear in the standard output when you run the Tester class?
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 1.   class Tester {
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 2.     int var;
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 3.     Tester(double var) {
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 4.       this.var = (int)var;
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 5.     }
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 6.     Tester(int var) {
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 7.       this("hello");
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 8.     }
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 9.     Tester(String s) {
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10.       this();
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11.       System.out.println(s);
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12.     }
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13.     Tester() {
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14.       System.out.println("good-bye");
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15.     }
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16.     public static void main(String args[]) {
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17.       Tester t = new Tester(5);
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18.     }
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a.  "hello"
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b.  5
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c.  "hello" followed by "good-bye"
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d.  "good-bye" followed by "hello"
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Q32
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What are the range of values for a variable of type short?
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a.  -2^7 to 2^7-1
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b.  0 to 2^8
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c.  -2^15 to 2^15-1
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d.  -2^15-1 to 2^15
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Q33
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Analyze the following two classes
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1.   class First {
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2.     static int a = 3;
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3.   }
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4.   final class Second extends First {
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5.     void method() {
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6.       System.out.println(a);
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7.     }
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8.   }
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a.  Class First compiles, but class Second does not.
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b.  Neither class compiles.
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c.  Both classes compile, and if method() is invoked, it writes 3 to the output.
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d.  Both classes compile, and if method() is invoked, it throws an exception.
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Q34
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What String instance method would return true when invoked as follows?
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1.   a.method(b);
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where a equals "GROUNDhog" and b equals "groundHOG"?
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a.  equals()
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b.  toLowerCase()
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c.  toUpperCase()
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d.  equalsIgnoreCase()
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Q35
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What access control keyword should you use to enable other classes to access a method freely within its package, but to restrict classes outside of the package from accessing that method? Select all valid answers.
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a.  private
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b.  public
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c.  protected
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d.  Do not supply an access control keyword (friendly).
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Q36
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What letters are written to the standard output with the following code?
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 1.   class Unchecked {
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 2.     public static void main(String args[]) {
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 3.       try {
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 4.         method();
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 5.       } catch(Exception e) { }
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 6.     }
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 7.     static void method() {
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 8.       try {
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 9.         wrench();
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10.         System.out.println("a");
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11.       } catch(ArithmeticException e) {
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12.           System.out.println("b");
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13.       } finally {
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14.           System.out.println("c");
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15.       }
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16.       System.out.println("d");
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17.     }
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18.     static void wrench() {
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19.       throw new NullPointerException();
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20.     } 
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21.   }
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 Select all valid answers.
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a.  "a"
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b.  "b"
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c.  "c"
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d.  "d"
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Q37
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If you would like to change the size of a Component, you can use the following method
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a.  size()
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b.  resize()
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c.  setSize()
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d.  dimension()
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Q38
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Which LayoutManager arranges components left to right and then top to bottom, centering each row as it moves to the next row?
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a.  BorderLayout
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b.  FlowLayout
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c.  GridLayout
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d.  CardLayout
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Q39
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Which label names(s) are illegal? Select all valid answers.
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a.  here
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b.  _there
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c.  this
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d.  2to1odds
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Q40
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Which keyword, when used in front of a method, must also appear in front of the class.
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a.  synchronized
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b.  abstract
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c.  public
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d.  private
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Q41
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 Given this code snippet,
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 1.   try {
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 2.     tryThis();
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 3.     return;
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 4.   } catch(IOException x1) {
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 5.     System.out.println("exception 1");
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 6.     return;
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 7.   } catch(Exception x2) {
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 8.     System.out.println("exception 2");
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 9.     return;
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10.   } finally {
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11.     System.out.println("finally");
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12.   }
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what will appear in the standard output if tryThis() throws a IOException?
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a. "exception 1" followed by "finally"
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b. "exception 2" followed by "finally"
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c. "exception 1"
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d. "exception 2"
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Q42
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Given the code snippet,
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1.   double a = 90.7;
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2.   double b = method(a);
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3.   System.out.println(b);
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if this snippet displays 90.0 in the standard output, what Math method did method() invoke? Select all valid answers.
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a.  abs()
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b.  round()
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c.  floor()
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d.  ceil()
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Q43
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What is written to the standard output given the following statement
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1.  System.out.println(4 | 7);
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a.  4
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b.  5
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c.  6
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d.  7
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Q44
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What expressions are true concerning the following lines of code?
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1.  int[] arr = {1, 2, 3};
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2.  for(int i = 0 ; i < 2; i++)
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3.    arr[i] = 0;
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Select all valid answers.
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a.  arr[0] == 0
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b.  arr[1] == 2
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c.  arr[1] == 0
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d.  arr[2] == 3
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Q45
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What will the following block of code write to standard output when it is executed?
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 1.   int i = 3;
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 2.   int j = 0;
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 3.   double k = 3.2;
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 4.   if (i < k)
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 5.      if (i == j)
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 6.         System.out.println(i);
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 7.      else
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 8.         System.out.println(j);
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 9.   else
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10.     System.out.println(k);
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a.  3
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b.  0
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c.  3.2
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d.  None of these.
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Q46
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What is the output of the following piece of code
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1.   int x = 6;
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2.   double d = 7.7;
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3.   System.out.println((x>d) ? 99.9 : 9);
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a.  9
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b.  9.0
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c.  99.9
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d.  Nothing, an ArithmeticException is thrown at line 3.
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Q47
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Which of the following are legal methods for the String class ?
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a.  length()
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b.  toUpper()
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c.  toUppercase()
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d.  equals()
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Q48
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Consider the following
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