📄 scjp 的一些笔记.htm
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System.out.print("exception ");<BR>
}<BR>
}<BR>4<BR>Catch处理最接近的异常，若在函数中有throw关键字抛出异常，则在本函数中有catch捕获到，则处理，不然就调用的时候被处理。如：<BR>public
class TestEx1<BR>{<BR> static void
test() throws RuntimeException<BR>
{<BR>
try<BR>
{<BR>
System.out.print("test
");<BR>
throw new
RuntimeException();<BR>
} catch (Exception ex)<BR>
{<BR>
System.out.print("exception ");<BR>
}<BR>
}<BR><BR> public static void
main(String[] args)<BR> {<BR>
try<BR>
{<BR>
test();<BR>
} catch (RuntimeException ex)<BR>
{<BR>
System.out.print("runtime ");<BR>
}<BR>
System.out.print("end ");<BR>
}<BR>}<BR>Print result: test exception
end<BR>5<BR>注意空指针异常，代码如：<BR>package exception;<BR><BR>public
class TestEx2<BR>{<BR><BR>
/**<BR> * @param
args<BR> */<BR>
public static void main(String[]
args)<BR> {<BR>
ClassA a = new
ClassA();<BR>
a.methodA();<BR><BR>
}<BR><BR>}<BR><BR>class ClassA<BR>{<BR>
public void methodA()<BR>
{<BR>
ClassB classB = new ClassB();<BR>
classB.getValue();<BR>
}<BR>}<BR><BR>class ClassB<BR>{<BR>
// public ClassC classC = new
ClassC();<BR> // classC = new
ClassC();<BR> public ClassC
classC;<BR><BR> public String
getValue()<BR> {<BR>
return
classC.getValue();<BR>
}<BR>}<BR><BR>class ClassC<BR>{<BR>
public String value;<BR><BR> public
String getValue()<BR> {<BR>
value =
"ClassB";<BR>
return value;<BR>
}<BR>}<BR><BR><BR><BR><BR>6<BR>数组要注意初始化，然后才可以付值
如下代码是错误的：<BR>注意抛：ExceptionlnlnitializerError<BR>public class
Foo {<BR>static int[] a;<BR>static { a[0]=2; }<BR>public
static void main( String[] args)
{}<BR>}<BR>7<BR>注意益出错误：StackOverflowError<BR>public class
ClassC<BR>{<BR><BR> public void
count(int i)<BR> {<BR>
count(++i);<BR> }<BR><BR>
public static void main(String[]
args)<BR> {<BR>
ClassC c = new
ClassC();<BR>
c.count(3);<BR><BR>
}<BR><BR>}<BR>8 <BR>StringBuff
类是线程安全的<BR>可以专换成StringBuild、用StingBuild执行更快。</DIV><BR
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<DIV class=t_msgfont id=message71960>9<BR>String
的方法应用：<BR>Substring(int start,int
end)用于取得一个字符传的子串，<BR>toUpperCase() 把字符串变成大写<BR>replace(int
start, int end, String str)<BR>delete(int start, int
end)<BR>多少个对象生产，但这个方法被调用：<BR>public String makinStrings()
{<BR>
String s = "Fred";<BR>
s = s + "47";<BR>
s = s.substring(2,
5);<BR>
s = s.toUpperCase();<BR>
return s.toString();<BR>
}<BR>答案是：3个<BR><BR>StringBuffer s = new
StringBuffer("123456789"); <BR>
s.delete(0,3).replace( 1,3,
"24").delete(4,6); <BR>
System.out.println(s);<BR><BR>输出s为：4247。<BR><BR>10<BR>基本类型转换的优先级大于自动装箱<BR>public
class Yikes {<BR><BR> public static
void go(Long n) {<BR>
System.out.println("Long ");<BR>
}<BR><BR> public
static void go(Short n) {<BR>
System.out.println("Short
");<BR> }<BR><BR>
public static void go(int n) {<BR>
System.out.println("int ");<BR>
}<BR>public static void main(String[] args) {<BR>
short y =
6;<BR>
long z = 7;<BR>
go(y);<BR>
go(z);<BR>
}<BR>}<BR>输出为：int
Long<BR><BR><BR><BR>11<BR>比较java.io.BufferedWriter与
java.io.FileWriter ,BufferedWriter里的方法多了个readline(),<BR>12
Serializable<BR>注意，使用的类没有序列化的话，进行序列化，若没有序列化该类会在运行时抛出异常/代码如：<BR>import
java.io.*;<BR>public class Forest implements Serializable
{<BR> private Tree tree = new
Tree();<BR> public static void
main(String[] args) {<BR>
Forest f = new Forest();<BR>
try {<BR>
FileOutputStream fs = new
FileOutputStream("Forest.ser");<BR>
ObjectOutputStream os = new ObjectOutputStream(fs);<BR>
os.writeObject(f);<BR>
os.close();<BR>
} catch (Exception ex) {<BR>
ex.printStackTrace();<BR>
}<BR>
}<BR>}<BR>class Tree
{<BR>}<BR>输入结果为：java.io.NotSerializableException:
serializable.Tree<BR>13 这个题目怎么做？？<BR>Question
101<BR>Assuming that the serializeBanana2() and the
deserializeBanana2() <BR>methods will correctly use Java
serialization and given:⌨️ 快捷键说明
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