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ObjectExample.java
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108 lines (90 loc) · 3.1 KB
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package class_ex;
/**
* 擴充 Object class，Object也是Java最高層級的類別。
*
* Object
* - String
* - Math
* - ...
* - ...
* - Scanner
*/
public class ObjectExample extends Object {
public static void main(String[] args) {
// example for using hasCode method.
hashCodeExample();
// compare with StringBuilder() and hasCode().
ObjectExample oe = new ObjectExample();
oe.useStringBuilder();
// example for using object and hasCode.
useObjectAndHashCode();
// check two objects is the same or not.
ObjectExample oe2 = new ObjectExample();
oe2.checkObjectExample();
}
public static void hashCodeExample() {
String msg1 = "台北";
String msg2 = "台中";
String msg3 = "台南";
String msg4 = "高雄";
String msg5 = "高雄";
int hc1 = msg1.hashCode();
int hc2 = msg2.hashCode();
int hc3 = msg3.hashCode();
int hc4 = msg4.hashCode();
int hc5 = msg5.hashCode();
System.out.println("[hashCodeExample] hc1: " + hc1);
System.out.println("[hashCodeExample] hc2: " + hc2);
System.out.println("[hashCodeExample] hc3: " + hc3);
System.out.println("[hashCodeExample] hc4: " + hc4);
System.out.println("[hashCodeExample] hc5: " + hc5);
}
/**
* 使用 StringBuilder 和 hashcode
*/
public void useStringBuilder() {
String msg1 = "台北";
StringBuilder msg2 = new StringBuilder("台中");
String msg3 = "台南";
StringBuilder msg4 = new StringBuilder("台南");
int hc1 = msg1.hashCode();
int hc2 = msg2.hashCode();
int hc3 = msg3.hashCode();
int hc4 = msg4.hashCode();
System.out.println("[useStringBuilder] hc1: " + hc1);
System.out.println("[useStringBuilder] hc2: " + hc2);
System.out.println("[useStringBuilder] hc3: " + hc3);
System.out.println("[useStringBuilder] hc4: " + hc4);
}
/**
* 結合 Object 和 hashCode
*/
public static void useObjectAndHashCode() {
NTUStudent ntu1 = new NTUStudent("Peter", 10);
int hc1 = ntu1.hashCode();
System.out.println("[useObjectAndHashCode] hc1: " + hc1);
}
/**
* 判斷物件是否相同
*/
public void checkObjectExample() {
NTUStudent ntu1 = new NTUStudent("George", 22);
NTUStudent ntu2 = new NTUStudent("George", 32);
NTUStudent ntu3 = ntu2;
System.out.println(ntu1.equals(ntu2)); // false
System.out.println(ntu1.equals(ntu3)); // false
System.out.println(ntu2.equals(ntu3)); // true
System.out.println(ntu1.toString() + "; <" + ntu1.getClass() + ">");
System.out.println(ntu2.toString() + "; <" + ntu2.getClass() + ">");
System.out.println(ntu3.toString() + "; <" + ntu3.getClass() + ">");
}
}
class NTUStudent extends Student {
NTUStudent(String name, int age) {
this.name = name;
this.age = age;
}
public String toString() {
return "Name: " + this.name + "; Age: " + this.age;
}
}