Guava – Objects 类
Objects类提供了适用于所有对象的辅助函数，如equals, hashCode等.
Objects 类声明
以下是com.google.common.base.Objects类的声明 −
@GwtCompatiblepublic final class Objects extends Object
Objects 类函数
| 序号 | 函数和描述 |
|---|---|
| 1 | static boolean equal(Object a, Object b) 判断两个可能为空的对象是否相等. |
| 2 | static <T> T firstNonNull(T first, T second) 废弃了。使用MoreObjects.firstNonNull(T, T)代替。这个方法计划在2016年6月被删除. |
| 3 | static int hashCode(Object... objects) 为多个值生成一个哈希代码. |
| 4 | static Objects.ToStringHelper toStringHelper(Class<?> clazz) 废弃了。使用MoreObjects.toStringHelper(Class)代替。这个方法计划在2016年6月被删除 |
| 5 | static Objects.ToStringHelper toStringHelper(Object self) 废弃了。使用MoreObjects.toStringHelper(Object)代替。这个方法计划在2016年6月被删除. |
| 6 | static Objects.ToStringHelper toStringHelper(String className) 废弃了。使用MoreObjects.toStringHelper(String)代替。这个方法计划在2016年6月被删除. |
Objects 类继承
该类继承了以下类的方法 −
java.lang.ObjectObjects 类示例
在C:/ >Guava中使用你选择的任何编辑器创建以下java程序.
GuavaTester.java
import com.google.common.base.Objects;public class GuavaTester { public static void main(String args[]) { Student s1 = new Student("Mahesh", "Parashar", 1, "VI"); Student s2 = new Student("Suresh", null, 3, null); System.out.println(s1.equals(s2)); System.out.println(s1.hashCode()); System.out.println( Objects.toStringHelper(s1) .add("Name",s1.getFirstName()+" " + s1.getLastName()) .add("Class", s1.getClassName()) .add("Roll No", s1.getRollNo()) .toString()); }}class Student { private String firstName; private String lastName; private int rollNo; private String className; public Student(String firstName, String lastName, int rollNo, String className) { this.firstName = firstName; this.lastName = lastName; this.rollNo = rollNo; this.className = className; } @Override public boolean equals(Object object) { if(!(object instanceof Student) || object == null) { return false; } Student student = (Student)object; // no need to handle null here // Objects.equal("test", "test") == true // Objects.equal("test", null) == false // Objects.equal(null, "test") == false // Objects.equal(null, null) == true return Objects.equal(firstName, student.firstName) // first name can be null && Objects.equal(lastName, student.lastName) // last name can be null && Objects.equal(rollNo, student.rollNo) && Objects.equal(className, student.className); // class name can be null } @Override public int hashCode() { //no need to compute hashCode by self return Objects.hashCode(className,rollNo); } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public int getRollNo() { return rollNo; } public void setRollNo(int rollNo) { this.rollNo = rollNo; } public String getClassName() { return className; } public void setClassName(String className) { this.className = className; }}Objects 类验证结果
使用javac编译器编译该类，如下所示 −
C:\Guava>javac GuavaTester.java
现在运行GuavaTester来看看结果.
C:\Guava>java GuavaTester
查看结果.
false85871Student{Name=Mahesh Parashar, Class=VI, Roll No=1} 
