public class Cat { private String id; private String name; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Cat(String id, String name) { this.id = id; this.name = name; } private static void changeName(Cat cat){ cat.setName("other"); } public static void main(String[] args) { Cat cat = new Cat ("1","kitty"); changeName(cat); System.out.println(cat.getName()); } /* public class ParamTest { public static void main(String[] args){ // Test 1: Methods can't modify numeric parameters System.out.println("Testing tripleValue:"); double percent = 10; System.out.println("Before: percent=" + percent); tripleValue(percent); System.out.println("After: percent=" + percent); //Test 2: Methods can change the state of object parameters System.out.println("\nTesting tripleSalary:"); Employee harry = new Employee("Harry", 50000); System.out.println("Before: salary=" + harry.getSalary()); tripleSalary(harry); System.out.println("After: salary=" + harry.getSalary()); // Test 3: Methods can't attach new objects to object parameters System.out.println("\nTesting swap:"); Employee a = new Employee("Alice", 70000); Employee b = new Employee("Bob", 60000); System.out.println("Before: a=" + a.getName()); System.out.println("Before: b=" + b.getName()); swap(a, b); System.out.println("After: a=" + a.getName()); System.out.println("After: b=" + b.getName()); } private static void swap(Employee x, Employee y) { Employee temp = x; x=y; y=temp; System.out.println("End of method: x=" + x.getName()); System.out.println("End of method: y=" + y.getName()); } private static void tripleSalary(Employee x) { x.raiseSalary(200); System.out.println("End of method: salary=" + x.getSalary()); } private static void tripleValue(double x) { x=3*x; System.out.println("End of Method X= "+x); } } Testing tripleValue: Before: percent=10.0 End of Method X= 30.0 After: percent=10.0 Testing tripleSalary: Before: salary=50000.0 End of method: salary=150000.0 After: salary=150000.0 Testing swap: Before: a=Alice Before: b=Bob End of method: x=Bob //可见引用的副本进行了交换 End of method: y=Alice After: a=Alice //引用本身没有交换 After: b=Bob */ }
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