我正在尝试使用哈希代码在 java 中运行程序，但我不断得到的结果是哈希代码中表达式的非法开始

Question

我正在尝试运行该程序，但不断收到非法开始表达式的错误，对哈希代码也知之甚少。 如何以正确的方式使用它，这段代码是什么意思？

public class Test1 {
 private int num;
 private String data;
 public boolean equals(Object obj) {
     if (this == obj)
         return true;
     if (obj == null) || (obj.getClass() != this.getClass())
     return false;
     //objects must be Test at this point
     Test test = (Test) obj;
     return num == test.num &&
         data == test.data || (data != null && data.equals(test.data));
 }
 public int hashCode() {
     int hash = 7;
     hash = 31 * hash + num;
     hash = 31 * hash + (null == data ? 0 : data.hashCode());
     return hash;
 }
}

Answer 1

你在equals方法中的括号对我来说看起来不对......

尝试

if(obj==null || (obj.getClass()!=this.getClass()))

您还需要将强制转换更改为正确的对象类型

Test1 test = (Test1)obj;

Answer 2

我在你的代码中看到了很多语法错误，请尝试在类下面。

        public class Test1 {
        private int num;
        private String data;
        public Test1(int num, String data)  {
            this.num = num;
            this.data =data;
        }
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if ((obj == null) || (obj.getClass() != this.getClass()))
                return false;
            // Objects must be Test at this point.
            Test1 test = (Test1) obj;
            return num == test.num && data == test.data || (data != null && data.equals(test.data));
        }
        public int hashCode() {
            int hash = 7;
            hash = 31 * hash + num;
            hash = 31 * hash + (null == data ? 0 : data.hashCode());
            return hash;
        }

        public static void main(String[] args) {
            Test1 obj1 = new Test1(1,"one");
            Test1 obj2 = new Test1(2,"two");
            Test1 obj3 = new Test1(1,"one");
            Test1 obj4 = new Test1(2,"two");
            System.out.println(obj1.equals(obj2));
            System.out.println(obj1.equals(obj3));
            System.out.println(obj2.equals(obj3));
            System.out.println(obj2.equals(obj4));
        }
    }