求助，小问题 - 黑马程序员技术交流社区

public static void main(String[] args) {
String a = "abc";
String b = "abc";
String c = new String("abc");
String d = new String("abc");
String e = a;
String f = a+"";
System.out.println("a==b为"+(a==b));
System.out.println("a.equals(b)为"+a.equals(b));
System.out.println("a==c为"+(a==c));
System.out.println("a.equals(c)为"+a.equals(c));
System.out.println("c==d为"+(c==d));
System.out.println("c.equals(d)为"+c.equals(d));
System.out.println("e==a为"+(e==a));
System.out.println("e.equals为"+e.equals(a));
System.out.println("a==f为"+(a==f));
System.out.println("a.equals(f)"+a.equals(f));
System.out.println("c==f为"+(c==f));
System.out.println("c.equals(f)为"+c.equals(f));
}

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package java131107;
/*
*
* 对于字符串与非字符串来说，==与equals有什么区别？
*
* */
public class Equals {
public static void main(String[] args) {
int ia = 3;
int ib = 3;
int ic = 5;
String s1 = "string";
String s2 = "string";
String s3 = "String *********";
String s4= new String("string");
Can ca1 = new Can("Can 1");
Can ca2 = new Can("Can 2");
Can ca3 = new Can("can1");
System.out.println("整数的对比********************");
System.out.println("ia==ib " + (ia == ib)); // true 基本数据类型只比较值
System.out.println("ia==ic " + (ia == ic)); // false 相等为真
// 整数无equals法对比 System.out.println("ia equals ib "+(ia.equals(ib));
System.out.println("字符串的对比********************");
System.out.println("s1==s2 " + (s1 == s2)); //true 对引用型数据比较地址值同一个内地址
System.out.println("s1==s3 " + (s1 == s3)); //false 不同的地址
System.out.println("s1==s4 " + (s1 == s4)); //false 不同的内存地址
System.out.println("s1 equals s2 " + s1.equals(s2)); //true 内容相同
System.out.println("s1 equals s3 " + s1.equals(s3)); //false 同容不同
System.out.println("s1 equals s4 " + s1.equals(s4)); //true 内容不同
System.out.println("类对象的对比********************");
System.out.println("ca1==ca2 " + (ca1 == ca2)); //false 地址不同
System.out.println("ca1 equals ca2 " + ca1.equals(ca2));//false 地址不同
System.out.println("ca1==ca2 " + (ca1.equals(ca2))); //false 地址不同
System.out.println("ca1 equals ca3 " + ca1.equals(ca2)); //false 地址不同
ca1 = ca2;// 把 c2的引用给了才c1;
System.out.println("ca1==ca2 " + (ca1 == ca2)); //true 同一个对象,相同
System.out.println("ca1 equals ca2 " + (ca1.equals(ca2))); //true 同一个对象
}
}
class Can{ //定义一个类
String s;
public Can(String classname) {
this.s=classname;
System.out.println("类ca****"+classname);
}
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