1. 以java.lang.Integer类型为例,讲解8种类型
package javase.jingjie.BaoZhuangLei;
public class Integer01 {
public static void main(String[] args) {
System.out.println("int最小值:"+Integer.MIN_VALUE);
System.out.println("int最大值:"+Integer.MAX_VALUE);
System.out.println("byte最小值:"+Byte.MIN_VALUE);
System.out.println("byte最小值:"+Byte.MAX_VALUE);
Integer i1=new Integer(10);
Integer i2=new Integer("123");
System.out.println(i1+","+i2);
System.out.println(i1.toString()+","+i2.toString());
}
}
2. 关于Integer中常用的方法,返回数据类型值
package javase.jingjie.BaoZhuangLei;
public class Integer02 {
public static void main(String [] args) {
Integer i1=Integer.valueOf(10);
int i2=i1.intValue();
System.out.println(i2+1);
double i0=i1.doubleValue();
System.out.println(i0+1);
Double i00=Double.valueOf(20.9);
double i01=i00.doubleValue();
System.out.println(i00+" "+i01);
int age=Integer.parseInt("25");
System.out.println(age+1);
double price =Double.parseDouble("3.0");
System.out.println(price+1.0);
String s1=Integer.toBinaryString(10);
System.out.println(s1);
String s2=Integer.toHexString(10);
System.out.println(s2);
}
}
3. 三种类型相互转换:Integer(引用类型) ,int,String
package javase.jingjie.BaoZhuangLei;
public class Integer03 {
public static void main(String[] args) {
Integer i1=Integer.valueOf(10);
int i2=i1.intValue();
Integer i3=Integer.valueOf("10");
String s1=i3.toString();
int i4=Integer.parseInt("123");
String s2=10+"";
Integer i30=10;
int i31=i30;
System.out.println(i30+","+(i31+1));
m1(12);
System.out.println(m2(12,6)+1);
}
public static void m1(Object o) {
System.out.println(o);
}
public static int m2(Integer i1,Integer i2) {
return i1-i2;
}
}
4. 自动拆箱和自动装箱
package javase.jingjie.BaoZhuangLei;
public class Integer04 {
public static void main(String[] args) {
Integer i1=new Integer(10);
Integer i2=new Integer(10);
System.out.println(i1==i2);
System.out.println(i1.equals(i2));
Integer i3=128;
Integer i4=128;
System.out.println(i3==i4);
Integer i5=127;
Integer i6=127;
System.out.println(i5==i6);
Integer i7=-128;
Integer i8=-128;
System.out.println(i7==i8);
Integer i9=-128;
Integer i10=-128;
System.out.println(i9==i10);
Integer i11=-129;
Integer i12=-129;
System.out.println(i11==i12);
}
}