java.util.Objects工具类示例

java.util.Objects是java 1.7引入的，主要是对对象的一些常用操作，比如compare、equals/deepEquals、hash/hashCode、isNull/nonNull、requiredNonNull、toString这12个常用方法。

Student类

public class Student {
private String name;
private Integer age;

public Student(String name, Integer age) {
this.name = name;
this.age = age;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public Integer getAge() {
return age;
}

public void setAge(Integer age) {
this.age = age;
}

@Override
public int hashCode() {
return this.getAge();
}

@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;

Student other = (Student) obj;
//if (age != other.age)
//	return false;
if (name == null) {
if (other.name != null)
return false;
} else if (!name.equals(other.name))
return false;
return true;
}
}

测试类：

import java.util.Comparator;
import java.util.Objects;
import java.util.function.Supplier;

public class ObjectsTest {

public static void main(String[] args) {
Student obj_01 = new Student("zhangsan", 30);
Student obj_02 = new Student("zhangsan", 20);

// 1
System.out.println("01. Objects.compare----->" + Objects.compare(obj_01, obj_02, new Comparator<Student>(){
@Override
public int compare(Student o1, Student o2) {
return o1.getAge().compareTo(o2.getAge());
}
}));

// 2
System.out.println("02. Objects.deepEquals----->" + Objects.deepEquals(obj_01, obj_02));

// 3
System.out.println("03. Objects.equals----->" + Objects.equals(obj_01, obj_02));

// 4
Object[] obj_04 = new Object[]{obj_01, obj_02};
System.out.println("04. Objects.hash---->" + Objects.hash(obj_04));

// 5
System.out.println("05. Objects.hashCode---->" + Objects.hashCode(obj_01));

// 6
Object obj_06 = null;
System.out.println("06. Objects.isNull----->" + Objects.isNull(obj_06));

// 7
Object obj_07 = null;
System.out.println("07. Objects.nonNull---->" + Objects.nonNull(obj_07));

// 8
Object obj_08 = 1;
System.out.println("08. Objects.requireNonNull----->" + Objects.requireNonNull(obj_08));

// 9
Object obj_09 = 1;
System.out.println("09. Objects.requireNonNull----->" + Objects.requireNonNull(obj_09, "The object cann't be null."));

// 10
Object obj_10 = 1;
System.out.println("10. Objects.requireNonNull----->" + Objects.requireNonNull(obj_10, new Supplier<String>(){
@Override
public String get() {
return "The Object cann't be null...";
}
}));

// 11
Object obj_11 = "123";
System.out.println("11. Objects.toString----->" + Objects.toString(obj_11));

// 12
Object obj_12 = "222";
System.out.println("12. Objects.toString----->" + Objects.toString(obj_12, "234") + "<----->" + Objects.toString(null, "234"));
}

}

运行结果：

01. Objects.compare----->1
02. Objects.deepEquals----->true
03. Objects.equals----->true
04. Objects.hash---->1911
05. Objects.hashCode---->30
06. Objects.isNull----->true
07. Objects.nonNull---->false
08. Objects.requireNonNull----->1
09. Objects.requireNonNull----->1
10. Objects.requireNonNull----->1
11. Objects.toString----->123
12. Objects.toString----->222<----->234