Integer的自动装箱与拆箱

Integer的自动装箱与拆箱

//Integer的自动装箱与拆箱
//JVM会自动缓存-128~127范围内的值 
public class IntegerDemo {
  public static void main(String[] args) {
    int a1=10;
    Integer a2=10;
    Integer a3=10;
    Integer a4=new Integer(10);
    
    int b1=1000;
    Integer b2=1000;
    Integer b3=1000;
    Integer b4=new Integer(1000);
    
    System.out.println(a1==a2);//true
    System.out.println(a1==a4);//true
    System.out.println(a2==a3);//true
    System.out.println(a2==a4);//false
    System.out.println("1--------");
    System.out.println(b1==b2);//true
    System.out.println(b1==b4);//true   
    System.out.println(b2==b3); //false
    System.out.println(b2==b4);//false    
    System.out.println("2--------");
    
    Integer c1=127,c2=128;    
    int c3=128;   
    c1=c3;//装箱
    
    System.out.println(c1==c2);//false
    System.out.println(c1==c3);//true
    System.out.println(c2==c3);//true
    
    System.out.println("3-----------");
    
    Integer d1=127;
    Integer d2=127;
    
    System.out.println(d1==d2);//true
    
    d1=128;
    d2=128;
    
    System.out.println(d1==d2);//false    
  }
}