Object类equals方法与“ == ”

闲话不说直接上例子:
（“ == ” 和 equals 返回的均为布尔类型）

例一：

String s1 = new String("abc");
String s2 = "abc";
System.out.println(s1 == s2);        	// 打印false
System.out.println(s1.equals(s2));     	// 打印true

例二：

String s1 = "abc";
String s2 = "abc";
System.out.println(s1 == s2);      	       //打印true
System.out.println(s1.equals(s2)); 	       //打印true

例三：

String s1 = "a" + "b" + "c";
String s2 = "abc"; 
System.out.println(s1 == s2);    		     //打印true
System.out.println(s1.equals(s2));	         //打印true

例四：

String s1 = "ab";
String s2 = "abc";
String s3 = s1 + "c";
System.out.println(s3 == s2);     	          //打印false
System.out.println(s3.equals(s2));   	       //打印true