单项选择题
Given this method in a class：
public String toString（） {
StringBuffer buffer = new StringBuffer（）；
buffer.append（‟<‟）；
buffer.append（this.name）；
buffer.append（‟>‟）；
return buffer.toString（）；
}
Which is true？（）
A. This code is NOT thread-safe.
B. The programmer can replace StringBuffer with StringBuilder with no other changes.
C. This code will perform well and converting the code to use StringBuilder will not enhance the performance.
D. This code will perform poorly. For better performance， the code should be rewritten： return “<“+ this.name + “>”；
相关考题
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单项选择题
11. class Converter { 12. public static void main（String[] args） { 13. Integer i = args[0]； 14. int j = 12； 15. System.out.println（”It is “ + （j==i） + “that j==i.”）； 16. } 17. } What is the result when the programmer attempts to compile the code and run it with the command java Converter 12？（）
A. It is true that j==i.
B. It is false that j==i.
C. An exception is thrown at runtime.
D. Compilation fails because of an error in line 13. -
单项选择题
public class TestString 1 { public static void main（String[] args） { String str = “420”； str += 42； System.out.print（str）； } } What is the output？（）
A. 42
B. 420
C. 462
D. 42042
E. Compilation fails.
F. An exception is thrown at runtime. -
单项选择题
1. public class Boxer1 { 2. Integer i； 3. int x； 4. public Boxer1（int y） { 5. x=i+y； 6. System.out.println（x）； 7. } 8. public static void main（String[] args） { 9. new Boxer1（new Integer（4））； 10. } 11. } What is the result？（）
A. The value “4” is printed at the command line.
B. Compilation fails because of an error in line 5.
C. Compilation fails because of an error in line 9.
D. A NullPointerException occurs at runtime.
E. A NumberFormatException occurs at runtime.
F. An IllegalStateException occurs at runtime.
