int定义的是简单32位整型变量
用Integer定义的对象变量,就有许多类的方法和属性可用了:public final class java.lang.Integer
extends java.lang.Number
{
// Fields
public final static int MAX_VALUE;
public final static int MIN_VALUE;
// Constructors
public Integer(int value);
public Integer(String s);
// Methods
public double doubleValue();
public boolean equals(Object obj);
public float floatValue();
public static Integer getInteger(String nm);
public static Integer getInteger(String nm, int val);
public static Integer getInteger(String nm, Integer val);
public int hashCode();
public int intValue();
public long longValue();
public static int parseInt(String s);
public static int parseInt(String s, int radix);
public static String toBinaryString(int i);
public static String toHexString(int i);
public static String toOctalString(int i);
public String toString();
public static String toString(int i);
public static String toString(int i, int radix);
public static Integer valueOf(String s);
public static Integer valueOf(String s, int radix);
}