Several common exceptions in java

##1.NullPointerException: Null pointer exception

Example:

public static void main(String[] args) {
String str = null;
//此处报空指针异常
System.out.println(str.length());
}

The exception information output by the console is:

Exception in thread "main" java.lang.NullPointerException
at cn.com.gjw.MyClass.main(MyClass.java:7)

2.ClassCastException: Type cast exception

Example:

public static void main(String[] args) {
// 类型强制转换异常
Object x = new String("String");
System.out.println((Integer) x);
}

The exception information output by the console is:

Exception in thread "main" java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Integer
at cn.com.gjw.MyClass.main(MyClass.java:7)

3.ArrayIndexOutOfBoundsException: Array subscript out-of-bounds exception

Example:

public static void main(String[] args) {
int arr[] = {1,2};
// 此处报数组下标越界异常
System.out.println(arr[2]);
}

The exception information output by the console is:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 2
at cn.com.gjw.MyClass.main(MyClass.java:7)

4.ArithmeticException : Arithmetic operation exception

Example:

public static void main(String[] args) {
// 整数0做了分母，报算术运算异常
System.out.println(1 / 0);
}

The exception information output by the console is:

Exception in thread "main" java.lang.ArithmeticException: / by zero
at cn.com.gjw.MyClass.main(MyClass.java:6)

5.NumberFormatException: Number format exception

Example:

public static void main(String[] args) {
// 将字符串“it”转换为Integer类型的，当然会报数字格式异常啦
System.out.println(Integer.parseInt("it"));
}

The exception information output by the console is:

Exception in thread "main" java.lang.NumberFormatException: For input string: "it"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
at java.lang.Integer.parseInt(Integer.java:492)
at java.lang.Integer.parseInt(Integer.java:527)
at cn.com.gjw.MyClass.main(MyClass.java:6)

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