📅  最后修改于: 2020-11-16 06:52:13             🧑  作者: Mango
Objects类提供适用于所有对象的帮助程序功能,例如equals,hashCode等。
以下是com.google.common.base.Objects类的声明-
@GwtCompatible
public final class Objects
extends Object
Sr.No | Method & Description |
---|---|
1 |
static booleanequal(Object a, Object b) Determines whether two possibly-null objects are equal. |
2 |
static Deprecated. Use MoreObjects.firstNonNull(T, T) instead. This method is scheduled for removal in June 2016. |
3 |
static int hashCode(Object… objects) Generates a hash code for multiple values. |
4 |
static Objects.ToStringHelpertoStringHelper(Class> clazz) Deprecated. Use MoreObjects.toStringHelper(Class) instead. This method is scheduled for removal in June 2016 |
5 |
static Objects.ToStringHelpertoStringHelper(Object self) Deprecated. Use MoreObjects.toStringHelper(Object) instead. This method is scheduled for removal in June 2016. |
6 |
static Objects.ToStringHelpertoStringHelper(String className) Deprecated. Use MoreObjects.toStringHelper(String) instead. This method is scheduled for removal in June 2016. |
此类从以下类继承方法-
使用您选择的任何编辑器在C:/> Guava中创建以下Java程序。
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;
}
}
使用javac编译器编译类,如下所示:
C:\Guava>javac GuavaTester.java
现在运行GuavaTester以查看结果。
C:\Guava>java GuavaTester
查看结果。
false
85871
Student{Name=Mahesh Parashar, Class=VI, Roll No=1}