Java修改Integer变量值遇到的问题及解决

Integer a = 1000 ; 

     Integer b = 1000 ; 

     Integer c = 100 ; 

     Integer d = 100 ; 

     System.out.println(a == b); 

     System.out.println(c == d);

/**

          * Returns an {@code Integer} instance representing the specified

          * {@code int} value.  If a new {@code Integer} instance is not

          * required, this method should generally be used in preference to

          * the constructor {@link #Integer(int)}, as this method is likely

          * to yield significantly better space and time performance by

          * caching frequently requested values.

          *

          * This method will always cache values in the range -128 to 127,

          * inclusive, and may cache other values outside of this range.

          *

          * @param  i an {@code int} value.

          * @return an {@code Integer} instance representing {@code i}.

          * @since  1.5

          */

         public static Integer valueOf( int i) { 

             assert IntegerCache.high >= 127 ; 

             if (i >= IntegerCache.low && i <= IntegerCache.high) 

                 //当为-128和127之间时，并没有new一个Integer,而是从缓存中取 

                 return IntegerCache.cache[i + (-IntegerCache.low)]; 

             return new Integer(i); 

         }

public void ceshi(Integer integer){

     integer= 4444 ;

}

Integer shuzi= new Integer( 100 );

new Test55().ceshi(shuzi);

System.out.println(shuzi);

Integer shuzi= new Integer( 100 );

shuzi= 5000 ;

System.out.println(shuzi);

/**

  * The value of the {@code Integer}.

  *

  * @serial

  */

private final int value;

package com.com.test;

/**

  * Created by ***** 2018/6/29 9:18

  * java中Integer类型对于-128-127之间的数是缓冲区取的，

  *  所以用等号比较是一致的。但对于不在这区间的数字是在堆中new出来的。所以地址空间不一样，也就不相等。

  */

public class IntegerTest {

     public static void main(String[] args) {

         Integer a1 = Integer.valueOf( 60 );  //danielinbiti

         Integer b1 = 60 ;

         System.out.println( "1:=" +(a1 == b1));  //true

         Integer a2 = 60 ;

         Integer b2 = 60 ;

         System.out.println( "2:=" +(a2 == b2));   //true

         Integer a3 = new Integer( 60 );

         Integer b3 = 60 ;   // 装箱过程也就是Integer b3=Integer.valueOf(60)

         System.out.println( "3:=" +(a3 == b3));    //false

//        System.out.println("3:="+(a3.equals(b3)));   //true

         Integer a4 = 129 ; //大于127时，在堆中新建

         Integer b4 = 129 ;

         System.out.println( "4:=" +(a4 == b4));  //false

//        System.out.println("4:="+(a4.equals(b4)));    //true

     }

}