弱鸡求助，怎么就分析不明白呢？

package practice;

public class Testl {
    private static int count = 1;
   
    public static void main(String[] args) {
        
        Testl test = new Testl();
        
        String str = "abc";
        test.testString(str);
        
        A aA = test.new A(10,"456");
        aA.printValues();
        test.testRef(aA);
        aA.printValues();
        aA.a = 50;
        test.testRef(aA).printValues();
        aA.printValues();
        
        
    }
   
    public void testString(String str){
        String aStr = "abc";
        String bStr = "ab" + "c";
        String cStr = new String("abc");
        
        System.out.println((count++)+":"+(aStr.equals(cStr))+" "+(aStr==cStr));
        System.out.println((count++)+":"+(aStr.equals(bStr))+" "+(aStr==bStr));
    }
   
    public A testRef(A aRef){
        aRef.printValues();
        aRef.str = "ddd";
        aRef = new A(20,"987");
        aRef.printValues();
        return aRef;
    }
   
    class A{
        private int a = 5;
        private String str = "123";
        
        public A(int num,String str){
            a = num;
            this.str = str;
        }
        
        public void printValues(){
            System.out.println((count++)+":"+"a="+a+",str="+str);
        }
    }
}

控制台输出结果为：1:true false2:true true
3:a=10,str=456
4:a=10,str=456
5:a=20,str=987
6:a=10,str=ddd  -->从这里开始不明白了，求大佬帮忙分析分析
7:a=50,str=ddd
8:a=20,str=987
9:a=20,str=987 -------->迷，搞不懂
10:a=50,str=ddd ------->迷，搞不懂

[此贴子已经被作者于2018-5-19 12:01编辑过]