详解java==运算符和equals()方法的区别

public class Test {
 public static void main(String[] args) {
  int a = 5;
  int b = 5;
  String s1 = "helloJava";
  String s2 = "helloJava";
  String s3 = "hello"+"Java";
  String s4 = "hello";
  String s5 = "Java";
  String s6 = s4 + s5;
  String s7 = new String("helloJava");
  System.out.println("a==b?: "+(a==b));
  System.out.println("s1==s2?: "+(s1==s2));
  System.out.println("s1==s3?: "+(s1==s3));
  System.out.println("s1==s6?: "+(s1==s6));
  System.out.println("s1==s7?: "+(s1==s7));
  System.out.println("s1.equals(s6)?: "+(s1.equals(s6)));
  System.out.println("s1.equals(s7)?: "+(s1.equals(s7)));
 }
}

public class Person {
 private String name;//姓名
 private int age;//年龄
 private String idNum;//身份证号
 
 public Person() {
  super();
 }
 
 public Person(String name, int age, String idNum) {
  super();
  this.name = name;
  this.age = age;
  this.idNum = idNum;
 }

 //重写equals方法
 public boolean equals(Object obj){
  //如果两个对象是同一个对象，返回true
  if(this == obj){
   return true;
  }
  //obj是Person对象
  if(obj!=null && obj.getClass()==Person.class){
   Person p = (Person)obj;
   //并且身份证号相同才判断两个对象相等
   if(this.idNum.equals(p.getIdNum())){
    return true;
   }
  }
  return false;
 }

 public String getName() {
  return name;
 }

 public void setName(String name) {
  this.name = name;
 }

 public int getAge() {
  return age;
 }

 public void setAge(int age) {
  this.age = age;
 }

 public String getIdNum() {
  return idNum;
 }

 public void setIdNum(String idNum) {
  this.idNum = idNum;
 }

 public static void main(String[] args) {
  Person p1 = new Person("张三", 14, "zs14abc");
  Person p2 = new Person("张三2", 15, "zs14abc");
  Person p3 = new Person("张三", 14, "zs14abc2");
  System.out.println("p1.equals(p2)?: "+(p1.equals(p2)));
  System.out.println("p1.equals(p3)?: "+(p1.equals(p3)));
 }

}