{
"error": null,
"id": "12345",
"result": {
    "inventory": [{
        "history": [{
            "when": "2012-08-30T07:28:51Z",
            "changes": [{
                "removed": "",
                "added": "1",
                "field_name": "qty"
            },
            {
                "removed": "normal",
                "added": "major",
                "field_name": "popularity"
            }],
        "id": 474599,
        "alias": null
    }]
}

enter code here

public class Result {

private Map<String, List<Inventory>> inventory;

public Map<String, List<Inventory>> getBugs() {
    return inventory;
}

public void setBugs(Map<String, List<Inventory>> inventory) {
    this.inventory = inventory;
}

public class Inventory {

private String id;
private String alias;
private Map<String, List<History>> history;

public String getId() {
    return id;
}

public void setId(String id) {
    this.id = id;
}

public String getAlias() {
    return alias;
}

public void setAlias(String alias) {
    this.alias = alias;
}

public Map<String, List<History>> getHistory() {
    return history;
}

public void setHistory(Map<String, List<History>> history) {
    this.history = history;
}

public class History {

private String who;
private String when;
private Map<String, Changes> changes;

public String getWho() {
    return who;
}
public void setWho(String who) {
    this.who = who;
}
public String getWhen() {
    return when;
}
public void setWhen(String when) {
    this.when = when;
}
public Map<String, Changes> getChanges() {
    return changes;
}
public void setChanges(Map<String, Changes> changes) {
    this.changes = changes;
}