java零碎知识点整理（3）

package com.test.wx.testequals;

public class TestEquals {

  public static void testEquals() {
    String a = "a";
    String b = "a";
    boolean result = a.equals(b);
    System.out.println(result);  // true
    System.out.println(a.hashCode() == b.hashCode());  // true
  }

  public static void testEqual() {
    String a = "a";
    String b = "a";
    if (a == b) {  // true
      System.out.println("true");
      System.out.println(a.hashCode() == b.hashCode());
    } else {
      System.out.println("false");
    }
  }

  public static void testEquals2() {
    String a = "a";
    String b = a;
    // equals方法比较两个对象的hashcode,hashcode即对象的地址
    System.out.println(a.equals(b));
    // == 比较两个变量或者对象的值是否相等，equals比较两个对象的引用是否相等（是否指向同一个对象）
    System.out.println(a==b);
  }

  public static void normalTest() {
    int a = 12;
    String b = String.valueOf(a);
  }

  public static void testObjectHashcode() {
    User user1 = new User(1, "test");
    User user2 = new User(2, "test");
    System.out.println("user1 toString: "+user1);
    System.out.println("user1 hashcode: "+user1.hashCode());
    // hashcode即是对象地址的十进制形式
    System.out.println(Integer.valueOf("659e0bfd", 16));
    System.out.println(user2);
  }

  public static void hexToDeciaml() {
    long a = 1021653256;
    System.out.println(Long.toHexString(a));	//3ce53108
    System.out.println(Integer.valueOf("659e0bfd", 16));
  }

  public static void main(String[] args) {
//  testEquals();
//  testEqual();
//  testEquals2();
//  hexToDeciaml();
    testObjectHashcode();
  }

}

package com.test.wx.testenum;

public class EnumTest {

  PrinterType printType;
  enum PrinterType { INKJET, DOTMATRIX, LASER };
  public EnumTest(PrinterType pType) {
    printType = pType;
  }

  public static void main(String[] args) {
//  PrinterType pType = new PrinterType();
    EnumTest enumTest = new EnumTest(PrinterType.LASER);
    System.out.println(enumTest.printType);
  }
}