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DynamicFields.java
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152 lines (128 loc) · 3.94 KB
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package exceptions;
/**
* RUN:
* javac exceptions/DynamicFields.java && java exceptions.DynamicFields
* OUTPUT:
* null: null
* null: null
* null: null
*
* d: Value of d
* number: 47
* number2: 48
*
* df: d: New value of d
* number: 47
* number2: 48
* number3: 11
*
* df.getField("d") New value of d
* exceptions.DynamicFieldsException
* at exceptions.DynamicFields.setField(DynamicFields.java:101)
* at exceptions.DynamicFields.main(DynamicFields.java:141)
* Caused by: java.lang.NullPointerException
* at exceptions.DynamicFields.setField(DynamicFields.java:102)
* ... 1 more
*/
// import java.util.logging.*;
// import java.io.*;
public class DynamicFields {
private Object[][] fields;
public DynamicFields(int initialSize) {
fields = new Object[initialSize][2];
for (int i = 0; i < initialSize; i++) {
fields[i] = new Object[] {null, null};
}
}
public String toString() {
StringBuilder result = new StringBuilder();
for (Object[] obj : fields) {
result.append(obj[0]);
result.append(": ");
result.append(obj[1]);
result.append("\n");
}
return result.toString();
}
private int hasField(String id) {
for (int i = 0; i < fields.length; i++) {
if (id.equals(fields[i][0])) {
return i;
}
}
return -1;
}
private int getFieldNumber(String id) throws NoSuchFieldException {
int fieldNum = hasField(id);
if (fieldNum == -1) {
throw new NoSuchFieldException();
}
return fieldNum;
}
private int makeField(String id)
{
for (int i = 0; i < fields.length; i++) {
if (fields[i][0] == null) {
fields[i][0] = id;
return i;
}
}
//
Object[][] tmp = new Object[fields.length+1][2];
for (int i = 0; i < fields.length; i++) {
tmp[i] = fields[i];
}
for (int i = fields.length; i < tmp.length; i++) {
tmp[i] = new Object[] {null, null};
}
fields = tmp;
return makeField(id);
}
public Object getField(String id) throws NoSuchFieldException {
return fields[getFieldNumber(id)][1];
}
public Object setField(String id, Object value) throws DynamicFieldsException
{
if (value == null) {
DynamicFieldsException dfe = new DynamicFieldsException();
dfe.initCause(new NullPointerException());
throw dfe;
}
int fieldNumber = hasField(id);
if (fieldNumber == -1) {
fieldNumber = makeField(id);
}
Object result = null;
try {
result = getField(id);
}
catch(NoSuchFieldException e) {
throw new RuntimeException(e);
}
fields[fieldNumber][1] = value;
return result;
}
public static void main(String[] args)
{
DynamicFields df = new DynamicFields(3);
System.out.println(df);
try {
df.setField("d", "Value of d");
df.setField("number", 47);
df.setField("number2", 48);
System.out.println(df);
df.setField("d", "New value of d");
df.setField("number3", 11);
System.out.println("df: " + df);
System.out.println("df.getField(\"d\") " + df.getField("d"));
Object field = df.setField("d", null);
}
catch(NoSuchFieldException e) {
e.printStackTrace(System.out);
}
catch(DynamicFieldsException e) {
e.printStackTrace(System.out);
}
}
}
class DynamicFieldsException extends Exception {}