一、代码如下
package www.wujianbotwo;
public class Demo12 {
public static void main(String[] args) {
// TODO Auto-generated method stub
try {
}catch(Exception e) {
}
}
}
package www.wujianbotwo;
public class Demo13 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Demo13 demo13= new Demo13();
//demo13.nullTest();
demo13.nullTestFour();
}
private void nullTest() {
// TODO Auto-generated method stub
try {
String s= null;
System.out.println("长度为：" + s.length());
}
catch(Exception e) {
System.out.println("您的字符串没有定义吧！！");
}
}
private void nullTestTwo() {
// TODO Auto-generated method stub
//try {
String s= null;
System.out.println("长度为：" + s.length());
//}
//catch(Exception e) {
// System.out.println("您的字符串没有定义吧！！");
//}
}
private void nullTestThree() {
// TODO Auto-generated method stub
try {
String s= null;
System.out.println("长度为：" + s.length());
}
catch(Exception e) {
System.out.println(e);
}
}
private void nullTestFour() {
// TODO Auto-generated method stub
try {
String s= null;
System.out.println("长度为：" + s.length());
}
catch(NullPointerException e) {
System.out.println(e);
System.out.println(e.getMessage());
System.out.println(e.getStackTrace());
}
}
}
package www.wujianbotwo;
public class Demo14 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Demo14 demo14= new Demo14();
demo14.nullTest();
}
private void nullTest() {
// TODO Auto-generated method stub
try {
String s= null;
//int x= 9 / 0;
System.out.println(s.length());
//System.out.println(x);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
package www.wujianbotwo;
public class Demo14 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Demo14 demo14= new Demo14();
demo14.nullTest();
}
private void nullTest() {
// TODO Auto-generated method stub
try {
String s= null;
//int x= 9 / 0;
System.out.println(s.length());
//System.out.println(x);
}
catch (ArithmeticException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (NullPointerException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
package www.wujianbotwo;
public class Demo14 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Demo14 demo14= new Demo14();
demo14.nullTest();
}
private void nullTest() {
// TODO Auto-generated method stub
try {
String s= null;
//int x= 9 / 0;
System.out.println(s.length());
//System.out.println(x);
}
catch (ArithmeticException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (NullPointerException e) {
// TODO Auto-generated catch block
//e.printStackTrace();
System.out.println(e);
System.out.println("字符变量没有初始化");
}
}
}