Integer 函数传参实现值交换

import java.lang.reflect.Field;

public class MainClass {
    public static void main(String[] args) {
        Integer a = 128;
        Integer b = -129;
        swarp(a,b);
        System.out.println(a);
        System.out.println(b);
        try {
            System.out.println("________________________________________________");
            swarp1(a,b);
            System.out.println(a);
            System.out.println(b);
            System.out.println("--------------------------------------------------");
            Integer c = 128;
            System.out.println(c);
            Integer d = new Integer(128);
            System.out.println("--------------------------------------------------");
            swarp2(a,d);
            System.out.println(a);
            System.out.println(d);
            
            
            
        } catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }
    public static void  swarp(Integer a, Integer b){
        Integer temp = a;
        a = b;
        b = temp;
    }
    
    public static void swarp1(Integer a, Integer b) throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException{
        Field field = a.getClass().getDeclaredField("value");
        field.setAccessible(true);
        Integer a1 = a;
        field.set(a, b);
        field.set(b, a1);
        field.setAccessible(false);
    }
    public static void swarp2(Integer a, Integer b) {
        Field field;
        try {
            field = a.getClass().getDeclaredField("value");
            field.setAccessible(true);
            int a1 = new Integer(a);
            field.set(a, b);
            field.set(b, a1);
            field.setAccessible(false);
        } catch (NoSuchFieldException | SecurityException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

private static class IntegerCache {
        static final int low = -128;
        static final int high;
        static final Integer cache[];

        static {
            // high value may be configured by property
            int h = 127;
            String integerCacheHighPropValue =
                sun.misc.VM.getSavedProperty("java.lang.Integer.IntegerCache.high");
            if (integerCacheHighPropValue != null) {
                try {
                    int i = parseInt(integerCacheHighPropValue);
                    i = Math.max(i, 127);
                    // Maximum array size is Integer.MAX_VALUE
                    h = Math.min(i, Integer.MAX_VALUE - (-low) -1);
                } catch( NumberFormatException nfe) {
                    // If the property cannot be parsed into an int, ignore it.
                }
            }
            high = h;

            cache = new Integer[(high - low) + 1];
            int j = low;
            for(int k = 0; k < cache.length; k++)
                cache[k] = new Integer(j++);

            // range [-128, 127] must be interned (JLS7 5.1.7)
            assert IntegerCache.high >= 127;
        }

        private IntegerCache() {}
    }

public static Integer valueOf(int i) {
        if (i >= IntegerCache.low && i <= IntegerCache.high)
            return IntegerCache.cache[i + (-IntegerCache.low)];
        return new Integer(i);
    }